Synology DS920+ Upgrade Guide: RAM, Drives and M.2 Cache

Lifecycle and support

A current model: sold new and supported.

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

RAM: one free slot, 8 GB total

The DS920+ comes with 4 GB of DDR4 memory. Synology's spec lists one user-accessible SO-DIMM slot and a maximum of 8 GB in total, so you add a single 4 GB module to the 4 GB already fitted. The base memory is described as onboard in Synology's Dutch datasheet, which suggests it is not the part you swap out.

Only non-ECC, unbuffered DDR4 SO-DIMM is supported. Synology's official module is the 4 GB D4NESO-2666-4G. It is sold as 2666, but Synology says modules run at the maximum frequency the CPU supports, so don't expect a 2666 rating to be the running speed. The exact running speed is not stated in Synology's documents.

Synology only lists a 4 GB module and gives no larger per-module limit. You may see reports of bigger third-party modules working, but those are unofficial and unverified here. Using a non-Synology module also means you don't get full warranty or technical support from Synology.

The slot is inside the unit on the right-hand side, so you need to remove the drive trays to reach it.

Buying tips

• For the safest route, buy Synology's own D4NESO-2666-4G.
• Make sure any module is DDR4, SO-DIMM, non-ECC and unbuffered. ECC and registered modules are not supported.
• Don't pay extra for a higher speed rating. The module runs at the CPU's maximum frequency.
• Treat modules larger than 4 GB as an unsupported experiment that could affect your warranty and support.

Storage: four SATA bays, two M.2 cache slots

The four front bays take 3.5 inch SATA hard drives or 2.5 inch SATA drives and SSDs. Synology lists 64 TB of raw internal capacity, based on four 16 TB drives. That is a quoted figure rather than a hard per-drive limit, but larger drives are not covered by it. The maximum single volume is listed as 108 TB. Synology's own branded options are the HAT5300 (3.5 inch HDD) and SAT5210 (2.5 inch SATA SSD). Synology's documents don't give a drive thickness limit for the bays.

The two M.2 2280 NVMe slots sit on the underside of the unit under two covers. Synology documents them as SSD cache slots (you create an SSD cache volume), not as general storage volumes, and they don't use the front bays. They are not hot-swappable, so shut the NAS down before changing those drives. Synology's SNV3410 is its branded M.2 NVMe option. The PCIe generation of the slots is not stated in Synology's documents, so don't count on a particular NVMe speed. Check current DSM support before relying on them for anything other than cache.

For more space, one DX517 expansion unit can be connected to the eSATA port, giving 9 bays in total. The DS920+ supports only one such unit, and the eSATA port is meant for expansion rather than general use. The unit has no memory card slot.

Buying tips

• Buy 3.5 inch drives for capacity, or 2.5 inch SATA drives if you want a quieter, lower-power setup.
• Plan the two M.2 slots as cache. Pick M.2 2280 NVMe drives only.
• Synology-branded drives are the safest match. Synology's documents don't say how other brands are handled.
• Buy matching drives where you can if you plan to build a multi-drive array.
• Buying drives larger than 16 TB is possible but falls outside Synology's quoted 64 TB figure.

How to upgrade

Before you start

• Back up everything important. Opening the unit and removing drives always carries some risk.
• Have your parts ready: a DDR4 non-ECC unbuffered SO-DIMM for RAM, or M.2 2280 NVMe drives for cache.
• Keep the owner's manual or Synology's hardware installation guide to hand for the exact steps.
• Work on a clean, static-free surface and note which tray goes in which bay if you remove drives.
• Remember that a non-Synology memory module means you don't get full warranty or technical support.

Steps

1. Back up your data
   Make sure your important files are backed up elsewhere before you open the NAS.
2. Shut down and unplug
   Shut the DS920+ down from DSM, then unplug the power and all other cables.
3. Ground yourself
   Touch bare metal or use an anti-static strap to discharge static before handling any part.
4. Remove the drive trays
   For RAM, pull out the drive trays to reach the empty memory slot on the inner right side. Note the bay order of your drives.
5. Fit the new part
   Insert the SO-DIMM into the empty slot. For M.2 cache drives, the slots are on the underside under two covers, so follow the installation guide for access.
6. Close up
   Refit any covers, slide the drive trays back into their original bays and reconnect the cables.
7. Power on and check
   Start the NAS and open Control Panel > Info Center. Total Physical Memory should show 8 GB if the new module is recognized. If you added M.2 drives, check they appear in DSM before creating an SSD cache.
8. If something is wrong
   If the memory is not detected, shut down, unplug and reseat the module. Try Synology's own module if you used a third-party one.

Good to know

• Larger third-party RAM modules are reported by some owners but are unofficial and unverified here.
• The running speed of the RAM is not stated exactly. Synology says modules run at the CPU's maximum frequency.
• The PCIe generation of the M.2 slots and the drive thickness limit of the bays are not stated in Synology's documents.
• The 64 TB raw capacity figure is based on 16 TB drives and is not a hard per-drive limit.
• Synology may revise the specification of the pre-installed memory for supply reasons, and says the revised parts are validated as equivalent.
• No CPU upgrade is documented for this model.

Frequently asked questions

How much RAM can the Synology DS920+ take?

Synology lists a maximum of 8 GB in total. The unit has 4 GB built in and one free SO-DIMM slot for a 4 GB module. Larger third-party modules are unofficial and unverified.

What type of RAM does the DS920+ use?

DDR4 SO-DIMM, non-ECC and unbuffered. Synology's own module is the D4NESO-2666-4G.

Can I use any 4 GB DDR4 SO-DIMM?

A module of the right type may work, but Synology does not give full warranty or technical support if you use a non-Synology module.

Can I use the M.2 slots as normal storage?

Synology documents them as SSD cache slots, not general storage volumes. Check current DSM support before planning around any other use.

Can I upgrade the CPU in a DS920+?

No CPU upgrade is documented. Synology lists an Intel Celeron J4125, and no swappable processor socket is described, so plan on the RAM and drive upgrades instead.

How many drives can a DS920+ hold?

Four in the unit, or 9 in total with one DX517 expansion unit connected over eSATA.

Official documents and references

• PDF Synology DS920+ Product Specifications
  Memory, drive options and DX517 expansion details
• PDF Synology DS920+ Hardware Installation Guide
  Memory slot location, drive trays and M.2 cache installation
• PDF Synology DS920+ Data Sheet
  Official hardware overview
• Synology DS920+ product page
  Bay, M.2 slot and memory slot summary