Synology DS925+: Specs, Drive Compatibility and Total Build Cost
The DS925+ is Synology's mainstream 4-bay Plus-series DiskStation. Below is what Synology's own spec sheet states about it, what it actually costs filled with drives at today's prices, and what its drive-compatibility list restricts and doesn't.
Hardware specifications, per Synology's own spec sheet
| Bays | 4 |
|---|---|
| Drive form factors | 4 x 3.5-inch SATA HDD or 2.5-inch SATA SSD |
| M.2 slots | 2 x M.2 2280 NVMe |
| M.2 purpose | SSD cache OR an independent M.2 storage pool |
| Max single-drive capacity | not published by Synology |
| RAM | DDR4 ECC SODIMM, 4GB installed (1 slot used of 2) |
| Network | 2 x 2.5GbE RJ-45 |
| Expansion unit | DX525 (1 unit) - 9 total bays |
| PSU | 100W |
| Published acoustic figure | 20.5 dB(A), Synology's own stated test method (idle, fully populated, 1m) |
Source: Synology DS925+ Product Specification, read 2026-09-14 — PDF.
Synology's own spec sheet lists both "SSD Read/Write Cache" and "M.2 SSD Storage Pool Support" as supported (not cache-only). M.2 bays are not hot-swappable, and pool use requires Synology-verified SSDs per Synology's own footnote.
The honest total: chassis + drives, three ways
$674.00 buys the empty chassis. Filling all 4 bays is the real purchase, and it costs differently depending on which tier of drive you choose - three genuinely different builds, not three versions of the same one.
Best value fill - DS925+ + 4 drives
Usable capacity by RAID level: RAID 1 20TB ($102.00/usable TB) · RAID 5 60TB ($34.00/usable TB) · RAID 6 40TB ($51.00/usable TB) · RAID 10 40TB ($51.00/usable TB) 5 items across 2 listings. In-stock listings only. Anything out of stock when this page loaded is named below rather than silently dropped.
| Item | Qty | Each | Line | |
|---|---|---|---|---|
| DriveMDD 20TB SATA 7200RPM NAS (20TB) | x4 | $509.99 | $2039.96 | Buy |
| ChassisSynology DiskStation DS925+ 4-Bay | x1 | $674.00 | $674.00 | Buy |
| Basket total | $2713.96 | |||
These are our current tracked prices. Amazon sets the seller and the final price at checkout - verify before you buy. Opening any item starts an Amazon session, and anything you add there is part of the same order - you do not need to come back here between items.
Enterprise fill - DS925+ + 4 drives
Usable capacity by RAID level: RAID 1 12TB ($110.00/usable TB) · RAID 5 36TB ($36.67/usable TB) · RAID 6 24TB ($55.00/usable TB) · RAID 10 24TB ($55.00/usable TB) 5 items across 2 listings. In-stock listings only. Anything out of stock when this page loaded is named below rather than silently dropped.
| Item | Qty | Each | Line | |
|---|---|---|---|---|
| DriveWD Ultrastar 12TB SATA HUH721212ALE601 (12TB) | x4 | $329.99 | $1319.96 | Buy |
| ChassisSynology DiskStation DS925+ 4-Bay | x1 | $674.00 | $674.00 | Buy |
| Basket total | $1993.96 | |||
These are our current tracked prices. Amazon sets the seller and the final price at checkout - verify before you buy. Opening any item starts an Amazon session, and anything you add there is part of the same order - you do not need to come back here between items.
Refurbished fill - DS925+ + 4 drives
Usable capacity by RAID level: RAID 1 2TB ($76.00/usable TB) · RAID 5 6TB ($25.33/usable TB) · RAID 6 4TB ($38.00/usable TB) · RAID 10 4TB ($38.00/usable TB) 5 items across 2 listings. In-stock listings only. Anything out of stock when this page loaded is named below rather than silently dropped.
| Item | Qty | Each | Line | |
|---|---|---|---|---|
| DriveToshiba MG03ACA200 2TB SATA Enterprise (2TB) | x4 | $38.00 | $152.00 | Buy |
| ChassisSynology DiskStation DS925+ 4-Bay | x1 | $674.00 | $674.00 | Buy |
| Basket total | $826.00 | |||
These are our current tracked prices. Amazon sets the seller and the final price at checkout - verify before you buy. Opening any item starts an Amazon session, and anything you add there is part of the same order - you do not need to come back here between items.
The smallest cheque that fills all 4 bays, separately from the value tiers above: 4 x Toshiba MG03ACA200 2TB SATA Enterprise at $104.98 each = $419.92. A smaller build, not a bigger discount.
Drive compatibility, measured
The DS925+ is the four-bay machine most of the 2025 coverage was written about, and the one where the reversal story matters most. Synology lists 22 hard drives for it and every one is its own, but the Plus tier is precisely the bucket where an unlisted drive still builds a pool. The list is short; the door is open.
117 third-party SATA HDDs in our own catalogue are fit-verified for this class of bay right now (interface, form factor and CMR-confirmed) - none of them is on Synology's own list, and on a Plus-tier machine that does not stop them working, only Unverified-labels them in DSM.
Full DS925+ compatible-drives page and Synology's drive policy, per series, dated.
Expansion limits and the M.2 reality
DX525 (1 unit) - 9 total bays - a DS925+ tops out at the bays it ships with unless a documented expansion path exists. Where one does, it is worth pricing before assuming a bigger array is a chassis swap away.
The M.2 slots are the trap worth naming specifically, because "my NAS has M.2 slots" means different things on different Synology models. On the DS925+, Synology's own spec sheet lists the two M.2 2280 slots as supporting BOTH an SSD read/write cache for the spinning array AND an independent M.2 storage pool - not cache-only. That is a genuine choice a buyer makes, not a foregone conclusion: a cache accelerates the existing HDD pool's reads and writes, while a storage pool is its own separate volume with its own capacity, unrelated to the HDD bays. Buying two M.2 SSDs expecting one behaviour and getting the other is an avoidable mistake, and Synology's own footnote adds a second constraint worth knowing before ordering: the storage-pool use case requires Synology-verified SSDs specifically, a narrower list than the HDD bays' own compatibility picture.
What else it needs
Power protection: a NAS writing during a power loss can corrupt a volume - see UPS units for a NAS, priced live with output waveform stated on every row. Networking: the DS925+'s two 2.5GbE ports are fixed - Synology documents no PCIe expansion slot for this model, so there is no vendor-documented path to 10GbE here the way there is on the DS1525+ and DS1825+ above it in the same line.
Frequently asked questions
Frequently asked questions
How many drives does the DS925+ take?
4, all 3.5-inch SATA HDD or 2.5-inch SATA SSD bays per Synology's own spec sheet. Plus two additional M.2 2280 NVMe slots that can run as cache or as their own storage pool.
What's the maximum capacity of the DS925+?
Synology's own spec sheet publishes no maximum single-drive capacity for this model - the large drive sizes on Synology's marketing page are used only to illustrate a raw-capacity total, not stated as a ceiling. With the DX525 expansion unit the chassis documents 9 total bays.
Can I use third-party drives in the DS925+?
Yes. Synology's own list for the DS925+ names 22 hard drives and every one is Synology's own HAT series - but the DS925+ is a Plus-tier machine, and on that tier an unlisted hard drive still creates a storage pool. DSM labels it Unverified rather than refusing it.
What does a complete DS925+ build cost?
$674.00 for the chassis alone; $2039.96 filled with 4 best-value drives, or as little as $419.92 for the smallest qualifying set. See the live basket below for the exact drives priced today.
Does the DS925+ support an expansion unit?
Yes - Synology documents the DX525 (1 unit) - 9 total bays.
Is the DS925+ RAM upgradeable?
Yes - DDR4 ECC SODIMM, 4GB installed (1 slot used of 2), and Synology's spec sheet states a maximum. Check the spec table above for the exact installed and maximum figures.
Sources checked: Synology DS925+ product page, Synology DS925+ Product Specification (PDF), Synology compatibility search.