Help Me Choose - Memory

Help Me Choose - Memory
PowerEdge offers a variety of memory options to meet your workloads requirements. Memory plays a key role in your overall performance along with your processor, accelerator and storage choices.

DDR5

Double Data Rate Type 5 is the newest DDR used in servers. 

DDR5 provides higher bandwidth and increased bandwidth efficiency. It offers a 50% increase in bandwidth with 4800 MT/s compared to DDR4 and supports a maximum density of 32 Gb. DDR5 also offers twice the burst length, twice the number of bank groups, and twice the number of banks.

DRAM stands for ‘dynamic random-access memory’ and is a type of memory we use in servers. DDR4, which stands for ‘double data rate generation four’, is the generation of memory used in 15G and previous-generation servers. DDR4 supports speeds up to 3200 MT/s.

DDR5 is the newest DDR version, offering significantly faster speeds, higher bandwidth, and increased bandwidth efficiency compared to DDR4. DDR5 includes the VR (voltage regulator) on the DIMM. DDR5 is used in 16G servers and beyond, while DDR4 is used in our 15G and previous-generation servers.

On-die ECC is an essential feature of DDR5. It provides protection by correcting single-bit errors within the DRAM chip itself before sending data to the CPU. This feature focuses on reliability within individual memory chips, ensuring higher reliability as memory density increases.

CXL Info

CXL Info with FAQ
Compute Express Link (CXL) is an open standard for high-speed low latency interconnect between the central processing unit and expansion devices that provide cache coherent memory. CXL memory devices add memory capacity and memory bandwidth beyond DDR alone. CXL memory can be used in addition to the required DDR5 DIMM memory.

CXL is only supported on 17G servers with limited configs
Form Factors include:
Add In Card single wide FHHL (full height half length)
Total Add-in Card Capacity: 384GB
PCIE lanes: x8 & x16

Please refer to the relevant platform sourcebook or contact your TSR (technical sales representative)
In R770 you can have 2x AIC (384GB each) and 1.5 TB of DDR5 DIMM memory.
In R7725 you can have 1x AIC (384GB) and 1.1 TB of DDR5 DIMM memory.

Frequently Asked Questions

Intel® Optane™ Persistent Memory is a unique technology that bridges a gap between ‘memory’ and ‘storage’. Like RAM it sits within the PC memory hierarchy. By placing commonly used data and programs closer to the processor, Intel® Optane™ Persistent Memory allows the systems to access this information more quickly and improve overall system responsiveness. Intel® Optane™ Persistent Memory is designed to work in conjunction with DRAM not replace DRAM. These two memory technologies complement each other within the system. If all DIMM slots are being used, 50% of the DIMM slots will have DRAM and 50% of the DIMM slots will have Intel® Optane™ Persistent Memory.

Because of Memory Mode, Intel® Optane™ Persistent Memory can be used with almost any workload. In memory mode, the DRAM is used as a cache layer and the Intel® Optane™ Persistent Memory appears as the system memory. Any application can be used with a supported operating system. This allows a server to have a large memory footprint at a very compelling cost point. Because any application can be used, virtualization is a great use case for memory mode. Intel® Optane™ Persistent Memory is not persistent in Memory Mode.

Optimizer Mode is the default standard option for mirroring there are no special configurations.

Full Memory Mirroring allows two memory regions to be created, and a write transaction occurs in both locations to back up the data. When data is read back, if the primary copy has an ECC failure that cannot be corrected, the secondary copy is used. Full Memory Mirroring reduces capacity by half.

Each write transition is executed in two locations. Full Memory Mirroring is ideal for environments with low tolerance for memory failure & mission-critical operations. While write performance will be reduced this approach ensures a redundant copy of the data is maintained.

FRM Mode is exclusively supported in a VMware environment. It represents a variant of full memory mirroring, wherein only a portion is mirrored. Typically, a kernel is placed within this mirrored portion, providing the benefits of resiliency and the consequences of mirroring. This can be a beneficial alternative to full memory mirroring when only critical software needs the additional redundancy since it costs less than mirroring all system memory. There are no additional benefits or drawbacks.

Depending upon configuration, Idle CXL Latency is up to 300ns.

Users guide will be available on week of April 11th on the product support pages at https://www.dell.com/poweredgemanuals

Dell advises against customers installing or removing CXL AIC or DIMMs from their systems. This process can be complex and may require specialized knowledge and tools to ensure it is done correctly and safely. To avoid potential damage to the system or voiding the warranty, it is recommended to contact the Dell support team for assistance.

Useful Resources

How to find the supported memory configuration guide for PowerEdge Servers.
DDR5 on AMD
Dell Next Generation PowerEdge Servers: Designed with DDR5 to Deliver Future-Ready Bandwidth
Memory Bandwidth for Next-Gen PowerEdge Servers Significantly Improved with Sapphire Rapids Architecture
Balanced Memory: Intel Xeon Scalable Processors on PowerEdge Servers
DDR5 Memory Bandwidth for Next-Generation PowerEdge Servers Featuring 4th Gen AMD EPYC Processors
Memory Channel Population