Dell PowerEdge R740xd Upgrade Guide: RAM, Drives and Storage

Lifecycle and support

No longer sold new. Supported until Dec. 31, 2028 (estimate).

Dates not listed haven't been published by the manufacturer or a reliable third party.

RAM: 24 DDR4 slots, registered ECC only

The R740xd has 24 full-size DDR4 DIMM slots with no soldered memory. It accepts registered ECC memory only: RDIMM and LRDIMM. Unbuffered desktop-style DIMMs are not supported. Dell also lists NVDIMM-N (16 GB modules) and Intel Optane DC persistent memory, but both are specialist options.

RDIMMs come in 8, 16, 32 and 64 GB sizes, giving up to 1,536 GB with two CPUs. LRDIMMs come in 64 GB (quad rank) and 128 GB (octa rank) sizes, giving up to 3 TB with two CPUs. With one CPU you get half the slots and half the capacity, so the maximum is 1.5 TB.

Speed: Dell's spec sheet quotes up to 2933 MT/s, which needs 2nd Generation Xeon Scalable CPUs. With 1st Generation CPUs, memory runs at 2666 MT/s. One Dell technical guide excerpt lists 2666 MT/s only, so check your CPU generation before paying extra for faster modules.

Dell's mixing rules: do not mix RDIMM and LRDIMM within a channel, controller, socket or across sockets. Do not mix 64 GB and 128 GB LRDIMMs. Do not mix 8 GB RDIMMs with NVDIMM-N. x4 and x8 DIMMs can be mixed within a channel. Persistent memory can be mixed with RDIMM or LRDIMM, but not in different operating modes (App Direct and Memory Mode) within or across sockets. Any NVDIMM-N setup needs two CPUs. Memory slots are not hot-pluggable, so shut the server down first.

Buying tips

• Buy registered ECC DDR4 only, and choose either RDIMM or LRDIMM for the whole server.
• Stick to the module sizes Dell lists (8, 16, 32, 64 GB RDIMM; 64 or 128 GB LRDIMM).
• Check whether you have 1st or 2nd Gen Xeon Scalable CPUs before paying for 2933 MT/s modules.
• Buy matching modules rather than mixing 64 GB and 128 GB LRDIMMs.
• With a single CPU, only half the slots are usable, so plan module sizes accordingly.

Storage: bays depend on your variant

The drive layout is fixed by the chassis and backplane, so the first job is to identify your exact variant. Dell lists these factory layouts: 12 x 3.5 inch at the front (12 drives), with optional 2 x 3.5 inch or 4 x 2.5 inch rear bays (14 or 16 drives), and optionally 4 x 3.5 inch mid bays (18 or 20 drives). The 24 x 2.5 inch front layout replaces the 3.5 inch front layout and can be extended with 4 rear bays (28 drives), or 4 mid and 4 rear bays (32 drives), all 2.5 inch. Mid and rear bays are present only on certain variants, and mid bays share chassis space with other components.

Front 2.5 inch bays take SAS, SATA or NVMe, but NVMe needs a backplane that supports it. Front 3.5 inch bays take SAS or SATA. Rear bays are SAS/SATA. NVMe in the mid bays appears only in Dell's older spec sheet, so don't count on it without checking your configuration. Dell's documents don't state that NVMe drives run at PCIe Gen3; the system's PCIe slots are Gen3, so that is the likely speed but it is unconfirmed.

For boot drives, the optional BOSS card holds two M.2 SATA SSDs (240 GB or 480 GB) with hardware RAID. There are no NVMe M.2 slots on the board. Dell's documents don't give the M.2 length; BOSS drives are normally 2280. The rear IDSDM/vFlash module has three microSD slots: two for IDSDM (16, 32 or 64 GB) and one for vFlash (16 GB), intended for hypervisor or boot use.

Dell's two spec sheet revisions disagree on maximum capacity for 3.5 inch bays: the newer one says 216 TB front, 64 TB mid and 32 TB rear, while the older one says 168, 56 and 28 TB, reflecting smaller maximum HDD sizes. Both give 184.32 TB for the 24 x 2.5 inch front bays. Dell's documents don't state drive thickness limits, so check the drive-carrier documentation before buying.

Buying tips

• Confirm your drive-count variant first; you can't add bays that your chassis doesn't have.
• Match the drive size and interface (2.5 or 3.5 inch, SAS, SATA or NVMe) to your backplane.
• For NVMe, make sure your backplane supports it; Dell's technical guide lists Samsung PM1735a and PM1733a drives.
• A BOSS card takes M.2 SATA drives only, not NVMe M.2.
• Check which storage controller you have (PERC, HBA330 and others are offered) before choosing drives.

How to upgrade

Before you start

• Find your exact drive-count variant and check which bays you actually have.
• Check which generation of Xeon Scalable CPU is fitted, as it sets your memory speed.
• Back up all data and note your RAID configuration.
• Download the owner's manual for the R740xd for exact disassembly steps.
• Have an anti-static wrist strap and a clear workspace ready.

Steps

1. Back up your data
   Make a full backup and note your RAID and BIOS settings before touching any hardware.
2. Power off and unplug
   Shut the server down properly, then unplug all power cables. Memory slots are not hot-pluggable, so the server must be off when you fit DIMMs.
3. Ground yourself
   Wear an anti-static strap or touch bare metal on the chassis, and handle parts by their edges.
4. Open the case
   Follow the owner's manual for removing the cover and any airflow shroud. Don't guess at latches or screws; the manual shows exactly how.
5. Install the part
   For memory, use the population order and mixing rules in Dell's memory guidelines and don't mix RDIMM and LRDIMM. For drives, fit them in the carriers and bays shown in the manual and match the interface to your backplane.
6. Close up and reconnect
   Refit any shroud and the cover, then reconnect cables and power.
7. Check the BIOS and firmware
   Power on and confirm the system sees the new memory total or drive. For drives, check your storage controller configuration too, as a new drive may need to be set up in RAID.

Good to know

• Dell's documents don't list a CPU compatibility chart for this server, so check the manual before buying a different processor. Memory speed depends on whether you have 1st or 2nd Generation Xeon Scalable CPUs.
• Dell's documents differ on maximum memory speed (2933 MT/s on the spec sheet, 2666 MT/s in one technical guide excerpt) and on maximum 3.5 inch capacities between spec sheet versions.
• NVMe drives probably run at PCIe Gen3, but Dell doesn't say so.
• Drive thickness limits aren't stated in Dell's documents, so check the drive-carrier documentation before buying.
• Dell doesn't publish model-wide end-of-support dates for the R740xd; look up your service tag on Dell Support for your unit's support status.

Frequently asked questions

How much RAM can the Dell PowerEdge R740xd take?

Up to 3 TB with two CPUs, using 24 x 128 GB LRDIMMs. With one CPU you get half the slots and half the capacity, so 1.5 TB. With RDIMMs the maximum is 1,536 GB with two CPUs.

What type of RAM does the R740xd use?

Registered ECC DDR4: RDIMM or LRDIMM. Unbuffered DIMMs are not supported.

Can I mix RDIMM and LRDIMM?

No. Dell says not to mix them within a channel, controller, socket or across sockets. You also shouldn't mix 64 GB and 128 GB LRDIMMs.

Does the R740xd support NVMe drives?

Yes, in 2.5 inch front bays, if your backplane supports NVMe. Dell's documents don't state the link speed; Gen3 is likely, as the system's PCIe slots are Gen3, but this is unconfirmed.

Can I add an M.2 SSD to the R740xd?

Only through the optional BOSS card, which holds two M.2 SATA SSDs (240 GB or 480 GB) with hardware RAID. There are no NVMe M.2 slots on the board.

Can I add more drive bays to my R740xd?

Not freely. The bay layout is set by the chassis and backplane. Mid and rear bays exist only on certain factory variants, so check your configuration.

Official documents and references

• Dell R740xd memory specifications
  Module types, sizes and maximum capacities
• Dell R740xd system memory guidelines
  Population and mixing rules
• Dell R740xd drive specifications
  Factory drive-count variants and layouts
• PDF Dell PowerEdge R740xd spec sheet (newer)
  Memory, bays, capacities and controllers
• PDF Dell PowerEdge R740xd spec sheet (older)
  Earlier capacity figures and mid-bay NVMe
• PDF Dell PowerEdge R740/R740xd technical guide
  NVMe drives, BOSS card and SD module details
• PDF Dell EMC PowerEdge R740xd technical specifications
  Full technical specifications PDF
• Dell R740xd manuals and documents
  Owner's manual and service documents