Lenovo ThinkSystem SR950 Server (Xeon SP Gen 2)

The Lenovo ThinkSystem SR950 server is designed for your most demanding, mission-critical workloads, such as in-memory databases, large transactional databases, batch and real-time analytics, ERP, CRM, and virtualized server workloads. Now supporting second-generation Intel Xeon Scalable Family processors, the powerful 4U ThinkSystem SR950 can grow from two to eight processors, and with 96 DIMM sockets, supports up to 24 TB of high-speed memory. The SR950 also now supports Intel Optane DC Persistent Memory for the ultimate in performance. The modular design of SR950 speeds upgrades and servicing with easy front or rear access to all major subsystems to maximize server availability.

The SR950 packs numerous fault-tolerant and high-availability features into a high-density, 4U rack-optimized design that reduces the space needed to support massive network computing operations and simplify servicing.

The following figure shows the Lenovo ThinkSystem SR950.

Figure 1. Lenovo ThinkSystem SR950

The SR950 server supports up to eight processors in a single 4U chassis. You can upgrade from a 2-socket system to an 8-socket system without having to replace the server enclosure or upgrade to a physically larger design. The SR950 offers enterprise scalability and advanced RAS features to support the most demanding mission-critical applications that require 24x7 operations.

The Lenovo ThinkSystem SR950 server is designed for your most demanding, CPU and memory intensive, mission-critical workloads, such as in-memory databases, large transactional databases, batch and real-time analytics, ERP, CRM, and virtualized server workloads. The powerful 4U ThinkSystem SR950 can grow from two to eight second-generation Intel Xeon Processor Scalable Family CPUs, delivering up to 36% total performance improvement over the first generation processor (based on Intel internal testing). The modular design of SR950 speeds upgrades and servicing with easy front and rear access to all major subsystems, to maximize server uptime.

Scalability and performance

The SR950 offers numerous features to boost performance, improve scalability, and reduce costs:

• Supports second-generation Intel Xeon Processor Scalable processors
• Dense server offering where up to 8 processors and 96 DIMMs are housed in only 4U of rack space.
• Offers a simple upgrade path that enables the server to be initially configured with as few as two processors and then later be upgraded to up to eight processors simply by adding a compute tray and system boards.
• Supports the Gold and Platinum level processors in the Intel Xeon Processor Scalable Family, including the "top bin" highest-performing 205 W processors available from Intel.
• Up to eight processors, each with up to 28 cores and 56 threads (for a total of up to 448 threads) to maximize the concurrent execution of multithreaded applications.
• Intelligent and adaptive system performance with Intel Turbo Boost Technology 2.0 allows processor cores to run at maximum speeds during peak workloads by temporarily exceeding processor TDP.
• Intel Hyper-Threading Technology boosts performance for multithreaded applications by enabling simultaneous multithreading within each processor core, up to two threads per core.
• Intel Virtualization Technology integrates hardware-level virtualization hooks that allow operating system vendors to better use the hardware for virtualization workloads.
• Intel Speed Select Technology provides improvements in server utilization and guaranteed per-core performance service levels with more granular control over processor performance.
• Intel Deep Learning Boost (Vector Neural Network Instruction set or VNNI) is designed to deliver significant, more efficient Deep Learning (Inference) acceleration for high-performance Artificial Intelligence (AI) workloads.
• Intel Advanced Vector Extensions 512 (AVX-512) enable acceleration of enterprise-class workloads, including databases and enterprise resource planning (ERP).
• Support for up to 96 TruDDR4 DIMMs operating at up to 2933 MHz means you have the fastest available memory subsystem and memory capacity of up to 24 TB using 96x 256 GB 3DS RDIMMs.
• Supports 2933 MHz Performance+ memory DIMMs which allow configurations of 2 DIMMs per channel to operate at the 2933 MHz rated memory speed.
• Supports the new Intel Optane DC Persistent Memory; up to 48 Data Center Persistent Memory Modules (DCPMMs) can be installed in conjunction with regular system memory. DCPMMs are up to 512 GB each, for a total of up to 24 TB of Persistent Memory.
• With both Persistent Memory and RDIMMs installed, the server supports up to a total of 36 TB of memory, 24 TB of Persistent Memory + 12 TB of regular system memory.
• Up to 24x 2.5-inch HDDs or SSDs provide a flexible and scalable all-in-one platform to meet your increasing demands.
• Of the 24x drive bays, support for up to 12 NVMe PCIe SSDs maximizes drive I/O performance, in terms of throughput, bandwidth, IOPS, and latency.
• The use of solid-state drives (SSDs) instead of, or along with, mechanical hard disk drives (HDDs), can improve I/O performance. An SSD can support up to 100 times more I/O operations per second (IOPS) than a typical HDD.
• New high-speed RAID controllers provide 12 Gb SAS connectivity to the drive backplanes. A variety of RAID adapters are available, with cache up to 8 GB and support for 12 drives on a single controller.
• Supports the Lenovo-patented M.2 adapter design for convenient operating system boot functions. Available M.2 adapters support either one M.2 drive, or two M.2 drives in a RAID 1 configuration, for the boot drive performance and reliability.
• The server has a dedicated flexible LAN-on-motherboard (LOM) slot offering a variety of 10 GbE or Gigabit Ethernet adapters that do not occupy one of the standard PCIe slots.
• A total of up to 17 rear-accessible PCIe slots: 14 general-purpose PCIe 3.0 slots plus slots dedicated to the LOM adapter and two ML2 adapters. In addition, the server has two internal slots for RAID or HBA adapters.
• The server offers PCI Express 3.0 I/O expansion capabilities that improve the theoretical maximum bandwidth by almost 100% (8 GTps per link using 128b/130b encoding) compared to the previous generation of PCI Express 2.0 (5 GTps per link using 8b/10b encoding).

Availability and serviceability

The SR950 is based on a modular service model where all components and options can be removed from the front or rear of the system, even parts that are located in the center of the machine such as fans, memory DIMMs, and processors. The SR950 is designed for 99.99% availability.

Watch the following video to show how easy it is to service the SR950 server:
https://lenovopress.com/lp0899-thinksystem-sr950-ease-of-service-video

The SR950 provides many features to simplify serviceability and increase system uptime:

• The server offers Single Device Data Correction (SDDC, also known as Chipkill), Adaptive Double-Device Data Correction (ADDDC, also known as Redundant Bit Steering or RBS), memory mirroring, and memory rank sparing for redundancy in the event of a non-correctable memory failure.
• The server offers hot-swap drives, supporting RAID redundancy for data protection and greater system uptime.
• The Dual M.2 Boot Adapter uses RAID-1 so that the two M.2 drives installed are configured as a redundant pair.
• The server has up to four hot-swap N+N redundant power supplies to help keep the server operational in the event of a power supply or utility supply failure.
• Each compute tray has 6 hot-swap N+1 redundant fans (a total of 12 fans when two compute trays are installed) to maximize availability for business-critical applications.
• The power source-independent light path diagnostics functionality provides individual light path LEDs that lead the technician to failed (or failing) components, which simplifies servicing, speeds up problem resolution, and helps increase system availability.
• The included LCD system information display panel provides greater diagnostic function by listing all error messages and VPD data needed for a service call, thereby speeding problem resolution and increasing system uptime.
• Proactive Platform Alerts (including PFA and SMART alerts): Processors, voltage regulators, memory, internal storage (SAS/SATA HDDs and SSDs, NVMe SSDs, M.2 storage, and flash storage adapters), fans, power supplies, RAID controllers, ambient temperature, and subcomponent temperatures. Alerts can be surfaced through the XClarity Controller to managers such as Lenovo XClarity Administrator, VMware vCenter, and Microsoft System Center. These proactive alerts let you take appropriate actions in advance of possible failure, thereby increasing server uptime and application availability.
• Solid-state drives (SSDs) offer more reliability than mechanical HDDs for greater uptime.
• The built-in XClarity Controller continuously monitors system parameters, triggers alerts, and performs recovery actions in case of failures to minimize downtime.
• Built-in diagnostics in UEFI, using Lenovo XClarity Provisioning Manager, speed up troubleshooting tasks to reduce service time.
• Lenovo XClarity Provisioning Manager supports diagnostic functions and collects service data to USB key drive or remote CIFS share folder for troubleshooting, to reduce servicing time.
• Auto-restart in the event of a momentary loss of AC power (based on power policy setting in the XClarity Controller service processor).
• Support for the XClarity Administrator Mobile app running on a supported smartphone and connected to the server through the service-enabled USB port, enables additional local systems management functions.
• Three-year or one-year customer-replaceable unit and onsite limited warranty, 9 x 5 next business day. Optional service upgrades are available.

Energy efficiency

The SR950 offers the following energy-efficiency features to save energy, reduce operational costs, and increase energy availability:

• The server can be used in environments up to ASHRAE A4 with ambient temperatures up to 45 °C.
• The server is Energy Star 3.0 compliant.
• Energy-efficient planar components help lower operational costs.
• High-efficiency power supplies with 80 PLUS Platinum certifications
• Intel Intelligent Power Capability powers individual processor elements on and off as needed, to reduce energy draw.
• Low-voltage 1.2 V DDR4 memory offers energy savings compared to 1.35 V and 1.5 V DDR3 DIMMs.
• Solid-state drives (SSDs) consume as much as 80% less power than mechanical 2.5-inch HDDs.
• The server uses hexagonal ventilation holes, which can be grouped more densely than round holes, providing more efficient airflow through the system.
• Optional Lenovo XClarity Energy Manager provide advanced data center power notification, analysis, and policy-based management to help achieve lower heat output and reduced cooling needs.

The following figure shows the front of the SR950 server.

Figure 2. Front view of the Lenovo ThinkSystem SR950

The following figure shows the rear of the SR950 server. The server has up to 17 PCIe slots, depending on the riser cards selected, and the number of processors installed.

Figure 3. Rear view of the Lenovo ThinkSystem SR950

The processors and other components are located on compute trays, the Upper Compute Tray and the Lower Compute Tray. Each compute tray holds up to four processors on two system boards. The compute trays are accessible from the front of the server, as shown in the following figure.

Figure 4. Lower Compute Tray partially removed

The server has one or two compute trays. Each compute tray contains:

• One or two compute system boards, each comprising:
  • Two processors
  • 24 DIMMs
• Six hot-swap fans, accessible even when the compute tray is installed
• 12x 2.5-inch hot-swap drive bays
• One PCIe slot reserved for a RAID adapter for internal SAS/SATA drives

The following figure shows the rear of the compute tray with its two compute system boards, one of them removed.

Figure 5. Compute tray with two compute system boards

The compute system board is shown in the following figure. Each system board holds two processors and 24 DIMM sockets, 12 per processor. The system board also has connections for the NVMe ports used to connect to the PCIe NVMe drive bays at the front of the server.

Figure 6. Compute system board

Processors installed in the compute system boards are numbered as shown in the following figure.

Figure 7. Processor numbering (viewed from the rear of the compute trays)

For some four-socket storage-rich configurations, a storage tray is used in the upper tray area instead of a compute tray. The following figure shows the key components of the storage tray.

Figure 8. Storage tray

All slots and ports at the rear of the server are housed in the I/O tray as shown in the following figure.

Figure 9. I/O tray

The following figure shows the architecture of the SR950 at a high level. The system boards with processors and memory are installed in compute trays along with the drive bays and storage adapter. The I/O board houses all onboard PCIe slots as well as the slots for the riser cards the offer the remaining PCIe slots.

Figure 10. SR950 architecture

The specific connections between system boards, processors and PCIe slots are dependent on the server configuration. This is described in detail in the Server configurations section. Specific processor-slot connections based on each configuration are described in the Slot availability by server configuration section.

The following figure shows System board 1 where processors 1 and 2 are installed. The slots on the I/O board are connected directly to these processors (or indirectly through the Intel C624 Platform Controller Hub, PCH).

Figure 11. System board 1 connections to the I/O board

The processors within the chassis communicate via UltraPath Interconnect (UPI) ports. These ports allow high speed communication between the CPUs. UPI replaces the Intel QuickPath Interconnect (QPI). One UPI link connects the two processors on each system board (UPI 3) and the other two UPI links are used to connect the other processors in adjacent boards to form four-way and larger systems.

In four-processor configurations, the design of the UPI links is either in a mesh or a ring topology. When a processor has 3 UPI ports, it can be used in a 4-socket mesh configuration where all processors are directly connected to every other processor. 5200 Series processors only have 2 UPI ports (ports 1 and 2) and therefore do not support mesh topology. These two UPI configurations are shown in the following figure.

Figure 12. Mesh (left) and Ring (right) topologies for four-socket configurations

Ring topology with 8200 Series processors: As discussed in the Server configurations section, the “Four-Socket Upgradable / Storage Rich” configuration is a four-socket configuration that uses a Ring topology but uses 8200 Series processors.

The server supports an 8-socket configuration (8200 Series processors required). The following figure shows the UPI links used to connect eight processors.

Figure 13. 8-socket topology

Refer to the processor options table for information on the number UPI links each processor option has for the SR950 system.

The SR950 supports five different configurations, depending on the desired number of processors, drive bays, PCIe slots, and upgradability to an 8-socket configuration.

Notes:

• The configurations listed here represent Lenovo's recommendations regarding the selection of compute system boards, I/O riser cards, and NVMe drive bays to maximize the available resources. You can select fewer drives and lower slot counts by using lower-slot-count riser cards to meet application requirements.
• The use of only two, three or six processors in configurations where supported will reduce the available I/O slots and NVMe drive bays. This is described in details in the Internal storage section and the I/O expansion options section.
• Configurations 1 and 2 support either two, three or four processors, however the use 5200 Series processors requires that four processors be selected. Two or three 5200 Series processors are not supported in these configurations due to the way the processors are connected.
• Configurations 3 and 4 are designed to be easily upgradable to 8 processors. As a result, 8200 Series processors are required.

When building a server in the configurator, the feature codes in the following table are key to selecting the right configuration.

Table 2. Server configurations

	Configuration 1. Four-Socket Performance The highest-performing 4-socket server, at the lowest cost, when up to 12 drives is enough, and without the need for a simple upgrade. Supports 2, 3 or 4 processors (if using 5200 Series processors, 4 processors must be selected). 4 sockets configured in mesh topology for best performance. 12 drive bays, 6 of which support NVMe drives (4 NVMe with 3 processors, and 2 NVMe with 2 processors). 15 rear PCIe slots with 4 processors (10 rear slots with 3 processors, and 6 rear slots with 2 processors). Filler installed in the upper tray area. Can be upgraded to 8S but requires the 4S Performance to 8S Upgrade Kit, additional components, and Lenovo hardware installation. Select feature codes AUNY and AX3Y.
	Configuration 2. Four-Socket Performance/ Storage Rich The highest-performing 4-socket server, when needing more than 12 drives without the need for a simple upgrade. Supports 2, 3 or 4 processors (if using 5200 Series processors, 4 processors must be selected). 4 processors configured in mesh topology for best performance. 24 drives, 12 of which support NVMe drives (8 NVMe with 3 processors, and 4 NVMe with 2 processors). 13 rear PCIe slots with 4 processors (9 rear slots with 3 processors, and 5 rear slots with 2 processors). Storage tray installed in the upper tray area. Can be upgraded to 8S but requires the 4S Performance to 8S Upgrade Kit, additional components, and Lenovo hardware installation. Select feature codes AUNY and AX3Z.
	Configuration 3. Four-Socket Upgradable The lowest-cost 4-socket server capable of a simple upgrade to 8 socket, and when 12 drive bays with 4 processors is enough storage. 2 or 4 processors, must be 8200 Series processors. 4 processors in a ring topology. 12 drive bays including up to 6 NVMe (2 NVMe with 2 processors). Up to 15 rear PCIe slots with 4 processors (6 rear slots with 2 processors). Filler installed in the upper tray area. Upgradable to 8-socket with an additional compute tray and two system boards. Once upgraded, the system will have 24 drive bays. Select feature codes AUKF and AX3Y.
	Configuration 4. Four-Socket Upgradable / Storage Rich 4-socket server capable of a simple upgrade to 8-socket, and needing more than 12 drive bays with 4 processors. Requires 4 processors, must be 8200 Series. 4 processors in a ring topology. 24 drive bays (including up to 4 NVMe). 10 rear PCIe slots. Two compute trays, with one system board in each tray. Upgradable to 8-socket with two additional system boards. Once upgraded, the server will support 12 NVMe drives. Select feature codes AUKF and AX3Z.
	Configuration 5. Eight-Socket Storage Rich Full featured 6- or 8-socket server with up to 24 drive bays, and the maximum number of PCIe x16 slots. Requires 6 or 8 processors, must be 8200 Series. 24 drive bays, 12 of which support NVMe drives (8 NVMe with 6 processors). 17 rear PCIe slots (13 rear slots with 6 processors installed). Two compute trays each with two system boards. Select feature codes AUKF and AX3Z.

The following table summarizes the configurations.

† If using 5200 Series processors, then 4 processors must be selected. Using two 5200 Series processors is not supported.
* Mesh topology requires a processor with 3 UPI connections; Processors such as the 5200 series with only 2 UPI connections will operate in Ring topology. See the table in the Processor options section.
‡ Upgrade requires the ThinkSystem SR950 4S Performance to 8S Upgrade Kit, 4TA7A10969. See the Server configuration upgrades section below.
** After upgrade, maximum storage will be 24 drives (12 NVMe), and up to 17 total PCIe slots available (may require replacement riser cards)

For details about PCIe slot availability based on each server configuration, see Slot availability by server configuration.

This section describes the system upgrades you can perform in the field. The upgrades are based on the configurations that are described in the Server configurations section.

Key components in the upgrades are listed in the following table.

4S Performance to 8S Upgrade Kit, 4TA7A10969, includes the following components:

• 4 mid-plane UPI & sideband interconnects

The Compute System Board option, 7XG7A03955, includes the following components:

• One compute system board v2, without processors or memory

The Upper Compute Tray Kit, 4C87A37049, includes the following components:

• 1x compute tray with 12 drive bays and 1 slot for storage adapter
• 6x 19K RPM system fans
• 1x compute system board
• 3x 4-bay drive bay fillers

Note: The Upper Compute Tray Kit does not include drive backplanes

The following table describes the before and after configurations and the components you will need to order to achieve the desired configuration.

* The Upper Compute Tray Kit includes 1x Compute System Board
** 8-socket configurations must use Intel Xeon Platinum (82xx) processors

Configuration notes:

• The added processors must match the processors already installed.
• When upgrading to Configuration 5 (8-socket configuration), Platinum-level (82xx) processors must be used, as listed in the Processor options section. Gold processors do not support 8-socket configurations.
• For best performance, each processor added should match the memory configuration of existing processors (number & size of DIMMs)
• The ThinkSystem SR950 4S Performance to 8S Upgrade Kit, 4TA7A10969, contains the mid-chassis interconnects needed for an 8-socket configuration, replacing the existing interconnects. Lenovo installation is highly recommended due to the complexity of this upgrade. Installation cost will vary depending on location and scope of work.

It is supported to upgrade an SR950 server with first-generation Intel Xeon Scalable processors to second-generation processors.

The process is as follows:

1. Order up to 8 processor options to replace the processors you have installed. If desired, order Intel Optane DC Persistent Memory modules.
2. Before swapping hardware, upgrade all system firmware to the latest levels, 19A or later
3. Replace the processors
4. Install Intel Optane DC Persistent Memory (if ordered)

Note: The ASHRAE support and environmental restrictions as outlined in the SR950 (Xeon SP Gen 1) product guide still apply to an upgraded server. See the following link for details:
https://lenovopress.com/lp0647#operating-environment

The following table lists the standard specifications.

The server is shipped with the following items:

• Rail kit
• Documentation flyer
• Power cords (model and region dependent)

ThinkSystem SR950 models can be configured by using the Lenovo Data Center Solution Configurator (DCSC).

Configure-to-order (CTO) models are used to create models with factory-integrated server customizations. For CTO models, two base CTO models are available for the SR950 as listed in the following table, CTO1WW and CTOLWW:

• The CTO1WW base CTO model is for general business and is selectable by choosing General Purpose mode in DCSC.
• The CTOLWW base model is intended for High Performance Computing (HPC) and Artificial Intelligence (AI) configurations and solutions, including configurations for Lenovo Scalable Infrastructure (LeSI), and is enabled using either the HPC & AI LeSI Solutions mode or HPC & AI Hardware mode in DCSC. CTOLWW configurations can also be built using System x and Cluster Solutions Configurator (x-config).

Preconfigured server models may also be available for the SR950, however these are region-specific; that is, each region may define their own server models, and not all server models are available in every region.

The following table lists the base CTO models of the ThinkSystem SR950 server.

The following tables list the available models, grouped by region.

• Models for Australia and New Zealand
• Models for South East Asian regions (ASEAN)
• Models for EMEA regions
• Models for India
• Models for Japan
• Models for USA and Canada

Refer to the Specifications section for information about standard features of the server.

The SR950 supports second-generation Intel Xeon Scalable processors in the Gold and Platinum levels.

Topics in this section:

• Continued support for 1st Gen Intel Xeon Scalable processors
• Memory capacity of processors
• Processor features
• Adding additional processors
• UEFI operating modes

The server supports up to four or eight processors, depending on the configuration selected, however processors are all installed within the 4U rack enclosure:

• The use of more than 4 processors requires a Platinum-level processor.
• For configurations that support up to eight processors, the server supports 2, 4, 6 or 8 processors.
• For configurations of up to four processors (lower cost configuration, no upgrade path to eight processors), the server supports 2, 3 or 4 processors.

As described in the Components and connectors section, processors and memory are located on compute system boards - one or two processors per board. Two system boards are installed in a compute tray, and there are two compute trays in the server. 

The table below lists the supported second-generation Intel processors.

All processors listed have the following characteristics:

• Second-generation Intel Xeon Scalable processors (formerly codenamed "Cascade Lake")
• 14 nm process technology
• Six DDR4 memory channels
• 48 PCIe 3.0 I/O lanes
• 1 MB L2 cache
• 1.375 MB or more L3 cache per core
• Intel Hyper-Threading Technology
• Intel Turbo Boost Technology 2.0
• Intel Advanced Vector Extensions 512 (AVX-512)
• Two or three Intel Ultra Path Interconnect (UPI) links at up to 10.4 GT/s

Some processors include a suffix letter in the processor model number:

• L: Large memory tier (supports total memory up to 4.5TB per processor)
• M: Medium memory tier (supports total memory up to 2TB per processor)
• N: NFV optimized
• S: Search optimized
• T: High Tcase
• U: Single socket
• V: VM Density optimized
• Y: Speed Select

Processors without a suffix, or those with a suffix other than M or L, support up to 1TB per processor.

For specifications of these processors, see the Intel Xeon Scalable Processor Reference for Lenovo ThinkSystem Servers:
https://lenovopress.com/lp1262-intel-xeon-sp-processor-reference#term=SKL

Memory capacity of processors

Second-generation Xeon Scalable processors are limited to the amount of memory they can address, as follows:

• Processors with an L suffix (eg 8280L): Up to 4.5 TB per processor
• Processors with an M suffix (eg 8280M): Up to 2 TB per processor (now withdrawn)
• All other processors: Up to 1 TB per processor

The calculation of the total memory per processor includes both the system memory DIMMs and the Persistent Memory DCPMMs installed in the server.

For example:

• A configuration using 12x 64GB DIMMs per processor is a total of 768 GB, which means that neither an M nor L processor is required
• A configuration using 12x 256GB DIMMs per processor is a total of 3 TB, which means that an L processor is required
• A configuration using 6x 32GB DIMMs + 6x 256GB DCPMMs is a total of 1.69 TB which means an M processor is required (an L processor may also be used)
• A configuration using 6x 64GB DIMMs + 6x 512GB DCPMMs is a total of 3.375 TB which means an L processor is required
• A configuration using 6x 256GB DIMMs + 6x 512GB DCPMMs is a total of 4.5 TB which means an L processor is required

The mesh and ring topologies are shown in the following figure.

Figure 14. Mesh and ring processor topologies

* L3 cache is 1.375 MB per core or larger. Processors with a larger L3 cache per core are marked with an *
** The Intel Xeon Gold 5218 and 5218B processors have similar specifications; however, they use different silicon designs and cannot be mixed in the same system.

Adding additional processors

For configurations with only one compute tray, you can upgrade to add a second compute tray. You can also add additional system boards as needed. The ordering information for these upgrades is listed in the following table.

The Upper Compute Tray Kit, 4C87A37049, includes the following components:

• 1x compute tray with 12 drive bays and 1 slot for storage adapter
• 6x 19K RPM system fans
• 1x Compute System Board v2
• 3x 4-bay drive bay fillers

Note: The Upper Compute Tray Kit does not include drive backplanes

The following table lists the feature codes that allow you to specify the mode you wish to preset in the factory for CTO orders.

The preset modes for the SR950 are as follows:

• Maximum Performance Mode (feature BFYB): Achieves maximum performance but with higher power consumption and lower energy efficiency.
• Minimal Power Mode (feature BFYC): Minimize the absolute power consumption of the system.
• Efficiency Favoring Power Savings Mode (feature BFYD): Maximize the performance/watt efficiency with a bias towards power savings. This is the favored mode for SPECpower benchmark testing, for example.
• Efficiency Favoring Performance Mode (feature BFYE): Maximize the performance/watt efficiency with a bias towards performance. This is the favored mode for Energy Star certification, for example.

For details about these preset modes, and all other performance and power efficiency UEFI settings offered in the SR950, see the paper "Tuning UEFI Settings for Performance and Energy Efficiency on Intel Xeon Scalable Processor-Based ThinkSystem Servers", available from https://lenovopress.lenovo.com/lp1477.

The SR950 with second-generation Intel Xeon Scalable processors uses Lenovo TruDDR4 memory operating at up to 2933 MHz. The server supports 12 DIMMs per processor, which corresponds to 48 DIMMs with four processors installed and 96 DIMMs when eight processors are installed. Each processor has six memory channels with two DIMMs per channel.

With 256 GB 3DS RDIMMs installed, an 8-socket server supports a total of 24 TB of system memory.

The SR950 with second-generation Intel Xeon Scalable processors also supports Intel Optane DC Persistent Memory, as described in the Persistent Memory section.

As described in the Components and connectors section, the memory is installed on compute system boards and there are two system boards per compute tray and one or two compute trays per server, depending on the configuration.

The SR950 with second-generation processors supports these memory DIMMs:

• 2666 MHz DIMMs, that operate at 2666 MHz both at 1 DIMM per channel and 2 DIMMs per channel
• 2933 MHz DIMMs, that operate at 2933 MHz at 1 DIMM per channel, and at 2666 MHz at 2 DIMMs per channel
• 2933 MHz Performance+ DIMMs, that operate at 2933 MHz both at 1 DIMM per channel and 2 DIMMs per channel

Note that if the processor selected has a memory bus speed of 2666 MHz, then all DIMMs will operate at 2666 MHz, even if the DIMMs are rated for 2933 MHz.

The following three tables lists the memory options that are available for SR950.

Lenovo TruDDR4 memory uses the highest quality components that are sourced from Tier 1 DRAM suppliers and only memory that meets the strict requirements of Lenovo is selected. It is compatibility tested and tuned to maximize performance and reliability. From a service and support standpoint, Lenovo TruDDR4 memory automatically assumes the system warranty, and Lenovo provides service and support worldwide.

For best performance, consider the following:

• Ensure the memory installed is at least the same speed as the memory bus of the selected processor.
• Populate memory DIMMs in quantities of 6 or 12 per processor, so that all memory channels are used.
• When mixing 16 GB and 32 GB DIMMs in the same configuration, use 16GB 2Rx8 DIMMs instead of 16 GB 1Rx4 DIMMs for better performance.
• Populate memory channels so they all have the same total memory capacity.
• Ensure all memory controllers on a processor socket have the same DIMM configuration.
• All processor sockets on the same physical server should have the same DIMM configuration.

The following memory protection technologies are supported:

• ECC
• SDDC (for x4-based memory DIMMs; look for "x4" in the DIMM description)
• ADDDC (for x4-based memory DIMMs)
• Memory mirroring
• Memory rank sparing

If memory channel mirroring is used, then DIMMs must be installed in pairs or sets of three (minimum of one pair or set of three per processor), and all DIMMs in the pair or set of three must be identical in type and size. 50% of the installed capacity is available to the operating system.

If memory rank sparing is used, then a minimum of two single-rank or dual-rank DIMMs must be installed per populated channel (the DIMMs do not need to be identical). In rank sparing mode, one rank of a DIMM in each populated channel is reserved as spare memory. The largest rank in the channel will be automatically selected as the spare rank. The amount of memory available to the operating system depends on the number, capacity and rank counts of the DIMMs installed.

The SR950 server supports Intel Optane DC Persistent Memory, a new class of memory and storage technology explicitly architected for data center usage. Persistent Memory offers significantly lower latency than fetching data from SSDs, even NVMe SSDs, and offers higher capacities than system memory.

Using Lenovo ThinkSystem servers running applications that are tuned for Intel Optane DC Persistent Memory will result in lower data latency compared to solid-state drive technology. When data is stored closer to the processor on nonvolatile media, applications can see significant overall improvement in performance. 

The following table lists the ordering information for the DC Persistent Memory modules (DCPMMs).

The following are the requirements when installing DCPMMs:

• All second generation Intel Xeon Scalable Family processors that the SR950 supports also support DCPMMs. First generation Xeon Scalable processors are not supported.
• All installed DCPMMs must be the same size. Mixing DCPMMs of different capacities is not supported
• Maximum 6 DCPMMs per processor (install 1 in each memory channel)
• Minimum 2 TruDDR4 DIMMs per processor (1 per memory controller)
• For Memory Mode, minimum 2 DCPMMs per processor (install 1 per memory controller)
• For App Direct Mode, minimum 1 DCPMM installed in the server (any processor)
• When either Memory Mode or Mixed Mode is used, the ratio of memory to DCPMMs must be between 1:16 and 1:4, but the recommended ratio is 1:4 for the best performance. For example, 6x 16GB DIMMs + 2x 256GB DCPMMs is a ratio of 1:5.33. This ratio requirement does not apply to App Direct mode.
• For each memory channel with both a DCPMM and a TruDDR4 DIMM installed, the DCPMM is installed in channel slot 1 (closest) and the DIMM is installed in channel slot 0
• To maximize performance, balance all memory channels
• In configurations with DCPMMs installed, memory mirroring is supported, with two restrictions:
  • Mirroring is only enabled on the DRAM DIMMs installed in the server; The DCPMMs themselves do not support mirroring.
  • Only App Direct mode is supported. Memory mirroring cannot be enabled when DCPMMs are in Memory Mode or Mixed Mode.
• Memory sparing is not supported with DCPMMs installed

DCPMMs offer the following memory protection technologies:

• ECC
• SDDC
• DDDC
• Patrol scrubbing
• Demand scrubbing

In the App Direct mode, the DCPMMs also support memory mirroring that is performed by the processor's integrated memory controllers. Memory mirroring is not supported in Memory Mode or Mixed Mode. Memory rank sparing is not supported by DCPMMs in any mode.

For more information, see the Intel Optane DC Persistent Memory (DCPMM) product guide, https://lenovopress.com/LP1066

The SR950 offers up to 24x 2.5-inch drive bays, depending on the server configuration selected (as described in Server configurations). The server also supports either one or two M.2 drives, installed in an M.2 adapter.

In this section:

• Backplanes and drive bays
• Adapters and cabling
• M.2 drives
• SED encryption key management with ISKLM

Backplanes and drive bays

Drives are all located at the front of the server, 12 drives at the front of the upper tray and 12 at the front of the lower tray. Drives are connected to 4-drive backplanes in a 2-by-2 configuration, as shown in the following figure. All drive bays are 2.5-inch form factor.

Figure 15. Location of backplanes

There are two different backplanes available for the SR950:

• SAS/SATA backplane: Supports 4 SAS or SATA drives
• AnyBay backplane:
  • Top two drives support SAS, SATA, or NVMe interface drives (Lenovo AnyBay)
  • Bottom two drive bays support SAS or SATA drives only

Regular 2.5-inch SAS/SATA drive bays support only SAS or SATA drives; however, the Lenovo AnyBay drive bay design allows a choice of SATA, SAS, or U.2 (NVMe) PCIe drives. This design enables the flexibility to configure some of the bays with high-performance PCIe SSDs while still using the other bays for high-capacity HDDs, which is an ideal solution for storage-tiering.

The part numbers in the following table include the cables needed for backplane field upgrades.

The backplane kits include the cables needed for 430 HBA and RAID 530/730/930 adapters, however for field upgrades using the RAID 940 adapter or 440 HBA, alternative cables are required and can be ordered using ThinkSystem SR950 X40 RAID Cable Kit, 4X97A80369. In CTO factory orders, the necessary cables will be derived.

If the server is configured with all AnyBay backplanes, then the server supports up to 12 NVMe drives, depending on the server configuration. The NVMe-capable drive bays are the even-numbered bays as shown in the following figure.

Figure 16. Drive bay numbering

The quantity and location of the AnyBay drive bays depends on the configuration, as listed in the following table.

See the Server configurations section for details about the five server configurations.

SAS/SATA backplanes are connected to the RAID adapter or HBA installed in the dedicated slot in that tray. AnyBay backplanes (NVMe support on 2 of the 4 drive bays) are connected to the RAID adapter or HBA or to an NVMe port adjacent to processor on a system board.

The following table lists which processor each SAS/SATA storage adapter and which NVMe port each backplane is connected to. Backplane numbering is shown in Figure 11.

Processor numbering is shown in Figure 7.

* See note below

The M.2 drives install into an M.2 adapter which in turn is installed in a dedicated slot on the system board. See the internal view of the server in the Components and connectors section for the location of the M.2 slot.

Supported drives are listed in the Internal drive options section.

For details about M.2 components, see the ThinkSystem M.2 Drives and M.2 Adapters product guide:
https://lenovopress.com/lp0769-thinksystem-m2-drives-adapters

The IBM Security Key Lifecycle Manager software is available from Lenovo using the ordering information listed in the following table.

The SR950 supports internal SAS and SATA drives with the addition of a RAID adapter or HBA. The adapter is installed in a dedicated slot in each compute tray. For NVMe support, the server uses NVMe ports that are on the compute system boards or on the storage tray if one is configured.

The following table lists the supported adapters.

* The RAID 730-8i 1GB Cache adapter is not available in USA and Canada.
** The 430-16i HBA and RAID 930-16i adapter support 12 drives when used in the SR950

For a comparison of the functions of the supported storage adapters, see the ThinkSystem RAID Adapter and HBA Reference:
https://lenovopress.com/lp1288-thinksystem-raid-adapter-and-hba-reference#sr950-support=SR950

The following tables list the drive options for internal storage of the server.

The server does not support any internal backup units.

The server supports the external USB optical drive listed in the following table.

The drive is based on the Lenovo Slim DVD Burner DB65 drive and supports the following formats: DVD-RAM, DVD-RW, DVD+RW, DVD+R, DVD-R, DVD-ROM, DVD-R DL, CD-RW, CD-R, CD-ROM.

The server supports the following PCIe slots, depending on the server configuration selected:

• Slots 1-17 are PCIe 3.0 slots accessible from the rear of the server
• One internal dedicated M.2 slot for an M.2 adapter located internally on the I/O tray
• Two internal dedicated PCIe 3.0 x8 slots for storage adapters, located internally in each compute tray or storage tray

The following figure shows the locations of the slots at the rear of the server.

Figure 18. PCIe 3.0 slots at the rear of the server

The 17 PCIe 3.0 rear-accessible slots are as follows:

• Slots 1-4 are via Riser Slot 1, one riser card of:
  • Riser with 4x PCIe 3.0 x16 slots, all full-height half-length, all 75W
  • Riser with 2x PCIe 3.0 x16 slots, all full-height half-length, both 75W
  • Riser with 4x PCIe 3.0 x8 slots, full-height half-length, all 75W
• Slot 5: PCIe 3.0 x16, low profile, 75W
• Slot 6: PCIe 3.0 x16, low profile, 75W
• Slot 7: PCIe 3.0 x8, low profile, 75W
• Slot 8: PCIe 3.0 x16 ML2, low profile (supports NC-SI)
• Slot 9: PCIe 3.0 x8 LOM adapter slot, low profile (supports NC-SI)
• Slots 10-15 are via Riser Slot 2, one riser card of:
  • Riser 5x16+ML2
    • Five PCIe 3.0 x16 slots, all full-height half-length, all 75W
    • One PCIe 3.0 x16 ML2 slot, full-height half-length, 30W (no NC-SI support)
  • Riser 2x16: Two PCIe 3.0 x16 slots, all full-height half-length, both 75W
  • Riser 4x8: Four PCIe 3.0 x8 slots, full-height half-length, all 75W
• Slot 16-17 on a riser:
  • PCIe 3.0 x8 low profile, 75W
  • PCIe 3.0 x8 low profile, 75W

Additional internal PCIe slots:

• One or two PCIe 3.0 x8 slots for storage adapters, one in each compute tray
• M.2 adapter slot

NC-SI (Network Controller Sideband Interface or NCSI) support means the primary port on the adapter installed in that slot can be configured as shared between XCC out-of-band management traffic and production Ethernet traffic.

For riser slots 1 and 2, the server supports the following three riser cards. These are shown in the figure below.

• Riser 5x16+ML2:
  • Five PCIe 3.0 x16 slots, all full-height half-length, all 75W
  • One PCIe 3.0 x16 ML2 slot, full-height half-length, 30W (no NC-SI support)

  Note: When the 5x16+ML2 riser is installed in riser slot 1, the bottom two slots (including the ML2) are not accessible and cannot be used.

• Riser 2x16: Two PCIe 3.0 x16 slots, all full-height half-length, both 75W
• Riser 4x8: Four PCIe 3.0 x8 slots, full-height half-length, all 75W

Figure 19. Riser cards for riser slots 1 and 2

• When installed in riser slot 1:
  • Riser 5x16+ML2 becomes slots 1-4 (bottom two slots inaccessible)
  • Riser 2x16 becomes slots 3-4
  • Riser 4x8 becomes slots 1-4
• When installed in riser slot 2:
  • Riser 5x16+ML2 becomes slots 10-15
  • Riser 2x16 becomes slots 12-13
  • Riser 4x8 becomes slots 10-13

Slots 16 and 17 are mounted on a single 2x8 riser card and are as follows:

• Slot 16: PCIe 3.0 x8, full-height half-length, 75W
• Slot 17: PCIe 3.0 x8, full-height half-length, 75W

The 2x8 riser card is shown below.

Figure 20. 2x8 riser card

Ordering information for the riser cards is listed in the following table.

Slot availability by server configuration

The riser cards required for each server configuration are listed in the following table. See the Server configurations section for details.

* If desired, the 4x8 or 2x16 riser cards can be used instead of the 5x16+ML2 riser, with reduced slot availability

Based on these riser card requirements, the available slots for each server configuration are highlighted with a grey background in the following table. The table also lists the processor that each PCIe slot is connected to, based on the server configuration selected. In the table, NC means not connected.

Processor numbering is shown in Figure 7.

* Slots 1 and 2 are not connected if the 2x16 riser card is used in riser slot 1
** In 2, 3 and 6 processor configurations, the following slots are not available:

• In 2-processor configurations, processors 3 and 4 are not installed; this means slots 1-4, slots 10-13, and slot 16 are not connected
• In 3-processor configurations, processor 3 is not installed; this means slots 10-13, and slot 16 are not connected
• In 6-processor configurations, processors 6 & 8 are not installed; this means slots 1-4 are not connected

The SR950 has an integrated 10Gb Ethernet controller, based on the Intel Ethernet Connection X722. The X722 has the following features:

• Integrated into the Intel PCH chipset
• Supports 1GbE or 10GbE connections, depending on the selected LOM Phy adapter
• Offers VXLAN/NVGRE hardware offloads
• Supports VMDq and SR-IOV for advanced virtualization
• Supports iWarp RDMA

To provide connectivity to the X722, the SR950 supports six different LOM (LAN on Motherboard) cards which provide the Ethernet PHY function. Only 1 LOM card can be installed. See Figure 3 for the location of the LOM slot.

The LOM card supports NC-SI to allow the network connection to be shared between the operating system and the XClarity Controller (XCC) management module. The LOM also supports Wake-on-LAN (WOL).

For more information about the X722 controller, see the Lenovo Press product guide:
http://lenovopress.com/lp0654-intel-x722-integrated-controller

The following table lists the supported LOM cards.

The SR950 also support one ML2 card for 4-socket configurations (slot 8). For 8-socket servers using the 5x16 ML2 riser, the server has two ML2 slots - slot 8 and slot 15. See the I/O expansion options section for details.

The ML2 card in slot 8 supports NC-SI however the ML2 card in slot 15 does not support NC-SI.

The following table lists the supported ML2 adapters.

The following table lists additional supported network adapters that can be installed in the regular PCIe slots.

* ThinkSystem servers do not support Features on Demand, so the Emulex VFA5.2 2x10 GbE SFP+ PCIe Adapter, 00AG570, cannot be upgraded to FCoE support. If you need FCoE or iSCSI support, use 00AG580 instead.

For more information, including the transceivers and cables that each adapter supports, see the list of Lenovo Press Product Guides in the Networking adapters category:
https://lenovopress.com/servers/options/ethernet

The following table lists the Fibre Channel HBAs supported by SR950.

For more information, see the list of Lenovo Press Product Guides in the Host bus adapters category:
https://lenovopress.com/servers/options/hba

The following table lists SAS HBAs and RAID adapters supported by SR950 server for use with external storage.

* Maximum is 4 adapters because there are only 4 supercap holders in the server, mounted on the side of the two riser cards.

For a comparison of the functions of the supported external storage adapters, see the ThinkSystem RAID Adapter and HBA Reference:
https://lenovopress.com/lp1288#sr950-support=SR950&internal-or-external-ports=External

For more information, see the list of Lenovo Press Product Guides in the Host bus adapters and RAID adapters categories:
https://lenovopress.com/servers/options/hba
https://lenovopress.com/servers/options/raid

The server supports the PCIe Flash Storage adapters listed in the following table.

For details about these adapters, see the Lenovo Press product guides in the Flash Adapters category:
https://lenovopress.com/servers/options/ssdadapter

Full-length adapter cards such as graphics processing units (GPUs) do not physically fit in the server and are not supported.

The SR950 uses a set of 60mm hot-swap single-rotor fans for system-wide cooling. Each compute tray or storage tray houses 6 hot-swap fans. The 6 fans in the compute tray are N+1 redundant, meaning that a single fan failure is tolerated in each compute tray.

Fans are located internal to the server immediately in front of the compute system boards, but are accessible from the front of the server by the long handle attached to the fan. As the handle is pulled out, the attached fan rotates from vertical orientation to horizontal orientation, allowing the fan to be removed from the system using the handle, as shown below.

Figure 21. Six fans installed in each compute tray (lower compute tray shown)

New SR950 servers with second-generation Intel Xeon Scalable processors will use 19K RPM fans. These faster fans ensure that all eight-socket configurations will run up to their supported ASHRAE ambient temperatures as stated in the Operating environment section.

The server supports up to four hot-swap power supplies. Power supplies are N+N redundant, which means that if the server has four power supplies installed, then the server can continue operation even with two failed power supplies, or if the utility service that feeds those two power supplies goes offline.

All power supplies installed in a server must have the same capacity (for example all 1600W).

The 1100W power supply is auto-sensing and supports both 110V AC (100-127V 50/60 Hz) and 220V AC (200-240V 50/60 Hz) power.

Note: At 100-127 V AC input, the 1100W power supply is limited to 1050W.

Power supply options do not include a power cord. For models of the SR950, the inclusion of a power cords is model dependent. Configure-to-order models can be configured without a power cord if desired.

See Physical and electrical specifications for additional information.

The server supports booting from an operating system or hypervisor installed on an M.2 solid-state drive. See the M.2 drives section for details and the list of available options.

You can download supported VMware vSphere hypervisor images from the following web page and load it on the M.2 drive using the instructions provided:
https://vmware.lenovo.com/content/custom_iso/

The server contains an integrated service processor, XClarity Controller (XCC), which provides advanced service-processor control, monitoring, and alerting functions. The XCC is based on the Pilot4 XE401 baseboard management controller (BMC) using a dual-core ARM Cortex A9 service processor.

Local management

The SR950 offers the front operator panel showing key LED status indicators, as shown in the following figure.

Figure 22. Front operator panel (LCD display panel closed)

The front operator panel pulls out (see the release latch in the above figure) to show an LCD display panel and buttons, as shown in the following figure. The LCD display panel allows quick access to system status, firmware, network, and health information.

Figure 23. LCD display panel

The LCD display and the function buttons give you access to the following information:

• Error messages
• System VPD: machine type & mode, serial number, UUID string
• System firmware levels: UEFI and XCC firmware
• XCC network information: hostname, MAC address, IP address, DNS addresses
• Environmental data: Ambient temperature, CPU temperature, AC input voltage, estimated power consumption
• System reset action

If an environmental condition exceeds a threshold or if a system component fails, XCC illuminates LEDs inside the server to help you diagnose the problem and find the failing part. The SR950 has fault LEDs next to the following components:

• Each processor
• Each memory DIMM
• Each system fan
• Each power supply
• Each rear-facing PCIe slot 
• Each drive bay

For local console use, the SR950 has both a front and rear VGA port. Only one can be active at a time. If displays are connected to both VGA ports, the front VGA port takes precedence. 

The steps to connect the mobile device are as follows:

1. Enable USB Management on the server, by holding down the ID button for 3 seconds (or pressing the dedicated USB management button if one is present)
2. Connect the mobile device via a USB cable to the server's USB port with the management symbol
3. In iOS or Android settings, enable Personal Hotspot or USB Tethering
4. Launch the Lenovo XClarity Mobile app

Remote management

The server offers a dedicated RJ45 port at the rear of the server for remote management via the XClarity Controller management processor. The port supports 10/100/1000 Mbps speeds.

Remote server management is provided through industry-standard interfaces:

• Intelligent Platform Management Interface (IPMI) Version 2.0
• Simple Network Management Protocol (SNMP) Version 3 (no SET commands; no SMNP v1)
• Common Information Model (CIM-XML)
• Representational State Transfer (REST) support
• Redfish support (DMTF compliant)
• Web browser - HTML 5-based browser interface with NLS support and using a responsive design that is suitable for all devices. Java and ActiveX are not required. 

IPMI via the Ethernet port (IPMI over LAN) is supported, however it is disabled by default. For CTO orders you can specify whether you want to the feature enabled or disabled in the factory, using the feature codes listed in the following table.