Dell PowerEdge R720 upgrade guide: RAM, storage and CPU

Lifecycle and support

Standard support ended on May 25, 2018 (estimate).

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

RAM: 24 sockets, ECC only, up to 768 GB

All memory is socketed - nothing is soldered - and there are 24 full-length DIMM sockets, 12 per CPU, arranged as four channels with three sockets each. The maximum is 32 GB per module and 768 GB in total, which you reach with 24 x 32 GB LRDIMMs in a dual-CPU system. Some memory vendors advertise higher totals using future modules; Dell validates 768 GB, so treat that as the real ceiling. What fits: ECC DDR3/DDR3L DIMMs only. ECC is mandatory and non-ECC desktop memory will not work. Dell supports ECC UDIMM, RDIMM (registered) and LRDIMM (load-reduced), but you cannot mix the types - one type for the whole machine. Registered RDIMMs are the practical choice for a good balance of price and capacity, and LRDIMMs are how you get to the top of the range. Limits and speed: 1866 MT/s is the top speed, but only with 1.5 V RDIMM/LRDIMM and an E5-2600 v2 processor. Original E5-2600 chips top out at 1600 MT/s, UDIMMs top out at 1600 MT/s, and 1.35 V parts run at 1600 or lower. If you mix speeds, every channel on both processors drops to the speed of the slowest DIMM, so it pays to buy matching sticks. Rank matters too: up to two quad-rank or three dual/single-rank DIMMs per channel, with LRDIMMs allowed three per channel. What to watch out for: population order matters. Fill the socket farthest from the processor in each channel first (the white-marked lever positions per channel), and put the highest-rank modules in the lowest-numbered sockets. Also note that the R720xd variant with 3.5-inch drives does not support LRDIMMs - Dell cites thermal limits - so that machine is capped at RDIMMs. Buying tip: buy a matched set of the same part number at the speed you want, and prefer 1.5 V RDIMM/LRDIMM if you are running a v2 CPU and want 1866 MT/s.

Buying tips

• Matched sticks of one type (RDIMM or LRDIMM) - never mix types or ranks of mixed speeds
• ECC DDR3/DDR3L only; non-ECC desktop DIMMs are not supported
• 32 GB LRDIMMs if you want the 768 GB maximum; RDIMMs are the everyday value pick

Storage: your bay count is a purchase decision

The R720 takes hot-plug SAS/SATA drives at 6 Gb/s in 2.5-inch or 3.5-inch form factors, depending on the chassis. The critical thing to know: the bay configuration is fixed when the server is built and cannot be changed later. The R720 comes in 8 x 2.5-inch, 16 x 2.5-inch, 8 x 3.5-inch, and 8 x 2.5-inch plus 4 Express Flash variants, while the R720xd offers 24 x 2.5-inch front (plus optional rear bays) or 12 x 3.5-inch front (plus optional rear bays). If you might want more bays someday, buy the larger chassis now. What fits: Dell's validated drives run up to 4 TB for 3.5-inch, 1.2 TB for 2.5-inch hard drives and 800 GB for SATA SSDs. Modern larger drives physically fit the bays but are not on Dell's validated list - people do use them, but you are on your own for support. Most used drives arrive bare, so budget for Dell drive caddies/trays. Limits and what to watch out for: there is no M.2 slot anywhere on this platform and no native NVMe - the backplane is SAS/SATA only. If you want NVMe, the only route is a third-party drive on a PCIe add-in card in one of the standard PCIe 3.0 slots, and boot support for that is not documented by Dell. The PCIe SSD 'Express Flash' bays (175 GB to 1.4 TB) exist only on the R720 chassis that includes them; the R720xd cannot use that option, despite what some resellers claim. For booting a hypervisor, Dell offers an Internal Dual SD Module (IDSDM) option - confirm availability on Dell's support page before ordering. Dell also lists PERC H310/H710/H710P RAID controllers (and H810 for external enclosures), including dual-RAID configurations on the split 16 x 2.5-inch chassis. Buying tip: decide your bay count first, then shop for drives that match the backplane (SAS or SATA, 2.5-inch or 3.5-inch), and order caddies at the same time. Remember the chassis is 755.8 mm deep, so you need a deep rack, and a fully loaded machine with two 130 W CPUs and 24 DIMMs draws significant idle power and fan noise.

Buying tips

• Buy the chassis with the bay count you will ever need - it cannot be upgraded
• Budget for drive caddies when buying used bare drives
• Validated capacities top out at 4 TB (3.5-inch), 1.2 TB (2.5-inch HDD) and 800 GB (SSD)

CPU: two Xeon E5-2600 sockets, up to 12 cores each

The R720 has two socketed Intel LGA2011 (Socket R) processor sockets. They accept Xeon E5-2600 (Sandy Bridge-EP) and E5-2600 v2 (Ivy Bridge-EP) chips, up to 12 cores and 24 threads per CPU, so a pair of top-bin parts gives you 24 cores and 48 threads. The example Dell gives for the top end is the E5-2697 v2 at 2.7 GHz with 30 MB cache and 8.0 GT/s QPI. Limits: the maximum supported thermal design power is 130 W per socket, and Dell's active heatsinks matched to the CPU's TDP class are required - a passive or wrong-class heatsink will not do. What to watch out for: v2 processors need a BIOS/firmware update first. On an older board a v2 chip may not POST at all until the firmware has been updated - typically you boot with an E5-2600 v1 installed, update, then swap in the v2. So if you are buying a v2 CPU for an unknown board, either confirm the firmware is current or plan the update around a v1 chip. Also note that faster memory (1866 MT/s) depends on having a v2 CPU, so a processor upgrade can unlock memory speed as well as cores. Buying tip: check which CPU is currently installed and what heatsinks and PSU configuration you have before ordering a 130 W part.

Buying tips

• Update the BIOS/firmware before fitting an E5-2600 v2 CPU
• Make sure you have Dell active heatsinks rated for the CPU's TDP class (up to 130 W)
• A v2 CPU is also what lets 1.5 V RDIMM/LRDIMM run at 1866 MT/s

How to upgrade

Before you start

• Back up anything you care about before touching memory, drives or the processor.
• Shut the server down properly and unplug the power cords. For drives, note that the bays are hot-plug, so a failed drive can usually be swapped with the system running - but memory and CPU work is always done powered off and unplugged.
• Ground yourself to discharge static - an anti-static strap or by touching the metal chassis before you handle any part. Memory and processors are static sensitive.
• Follow Dell's instructions for opening the case and removing any shrouds, risers or heatsinks. If your exact step is not described here, use the owner's manual for the disassembly details.
• Install the part: seat DIMMs firmly until the latches close (fill order matters - farthest socket in each channel first), slide drives into the caddies and bays, or fit the CPU in its socket with the matching heatsink.
• Close the case, reconnect the power, and start the server.
• Check that the BIOS/firmware sees the new part - total memory, drive in the boot/RAID configuration, and the CPU model and core count. For an E5-2600 v2 CPU, update the BIOS/firmware first if the board is not already current.

Steps

1. Back up your data
   Protect anything important before any hardware change.
2. Power off and unplug
   Shut the OS down and disconnect the power cords. Only hot-swap drives are designed for live changes.
3. Ground yourself
   Use an anti-static strap or touch the chassis to discharge static before handling DIMMs, drives or CPUs.
4. Open the case
   Follow Dell's owner's manual for the exact disassembly steps for your chassis.
5. Install the part
   Memory: fill the socket farthest from the CPU in each channel first. Drives: use proper caddies and the matching bay. CPU: matching Dell active heatsink required.
6. Close up and check the BIOS
   Reconnect power, boot, and confirm the firmware reports the new memory total, the drive, and the CPU.

Good to know

• Dell's documents support 768 GB maximum memory; one vendor lists 1.5 TB with future modules, which has never been validated for this server.
• Maximum memory speed is listed as 1866 MT/s in Dell's guide (a mirror of the same guide says 1600 MT/s). In practice 1866 MT/s needs 1.5 V RDIMM/LRDIMM and an E5-2600 v2 CPU.
• Express Flash PCIe SSD bays are a standard R720 option only; some resellers advertise them on the R720xd, which Dell's chassis table does not support.
• Drive height limits are not stated in Dell's documents for this model - check the drive's spec sheet against your tray before buying.

Frequently asked questions

How much RAM can the Dell PowerEdge R720 take?

Up to 768 GB in a dual-CPU system, using 24 x 32 GB LRDIMMs. There are 24 socketed DIMM slots, 12 per CPU. Some memory vendors advertise more with future modules, but 768 GB is the capacity Dell documents.

What type of memory does the R720 use?

ECC DDR3/DDR3L DIMMs only - UDIMM, RDIMM or LRDIMM, one type for the whole machine and no mixing. Non-ECC desktop memory is not supported. The R720xd with 3.5-inch drives cannot use LRDIMMs.

Does the R720 support NVMe or M.2 SSDs?

No M.2 slot and no native NVMe support. The drive bays are hot-plug SAS/SATA 6 Gb/s. The only NVMe route is a third-party drive on a PCIe add-in card, and Dell does not document boot support for that. The PCIe 'Express Flash' SSD bays exist only on certain R720 chassis.

What CPUs fit the R720?

Dual Intel LGA2011 (Socket R) Xeon E5-2600 and E5-2600 v2 processors, up to 12 cores each and up to 130 W per socket. Top-bin examples include the E5-2697 v2.

Do I need a BIOS update for an E5-2600 v2 CPU?

Yes, usually. v2 (Ivy Bridge-EP) chips need a BIOS/firmware update, and an older board may not POST with one until it is updated. Plan to boot with a v1 CPU installed to perform the update if needed.

Can I add more drive bays to my R720 later?

No. The drive chassis and bay count are fixed at purchase - the options include 8 or 16 x 2.5-inch, 8 x 3.5-inch and the Express Flash configuration on the R720, with larger layouts on the R720xd. Choose the bay count you need up front.

Official documents and references

• Dell PowerEdge R720 Owner's Manual - System memory
  Official memory layout, population rules and the R720xd LRDIMM restriction.
• PDF Dell PowerEdge R720/R720xd Reference Guide (PDF)
  Chassis and bay options, validated drive list, memory frequencies, CPU support and system specs.
• Dell PowerEdge R720/R720xd Getting Started Guide - Technical specifications
  Dimensions and physical requirements.
• Dell knowledge base - Supported memory configuration guide for PowerEdge servers
  Dell's general memory configuration guidance.
• Dell video - How to replace the RAM for PowerEdge R720 and R720xd
  Visual walk-through of memory replacement.