How much storage fits in the Synology DiskStation DS925+?
By Devin Chua · Data checked by Owen Nakamura · Updated The Synology DiskStation DS925+ takes 4 drives, up to 96 TB raw, but usable is the number that matters: 4 × 8 TB in SHR gives 21.83 TiB, and it survives 1 drive failing. The gap from raw capacity is parity, and SHR lets you grow with mixed drive sizes.
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CMR NAS drives for the DS925+, by price per TB
Only families with confirmed CMR recording and a 24/7 rating, in stock on Amazon.ca and sized for the DS925+. SMR drives are deliberately kept out.
What sets the DS925+ apart
The model the whole drive debate revolves around. Since DSM 7.3 you can fit ordinary NAS drives again, and with SHR the DS925+ makes good use of mixed drive sizes. Do not overlook: unlike the DS923+ it has no slot for a 10-gigabit card, but it ships with two 2.5-gigabit ports.
Who the DS925+ is for
The DS925+ runs the AMD Ryzen V1500B (4 cores, 8 threads), and Plex users need one fact first: these embedded Ryzens carry no integrated GPU, so the DS925+ cannot hardware-transcode video. It is built for a different job — Synology's app suite, Docker and genuine virtual machines, backed by 4 to 32 GB of ECC memory. Choose the DS925+ as a dependable ECC all-rounder; for hardware transcoding in this price band, an Intel-based UGREEN or QNAP is the better tool.
How the DS925+'s network shapes the drive choice
The DS925+ runs 2 × 2.5GbE. Two-and-a-half gigabit is about 280 MB/s — almost exactly what a modern high-capacity NAS drive reads off its outer tracks — so the DS925+ sits in the sweet spot where an ordinary CMR drive saturates the link and a Pro model buys nothing on speed. Drives under about 8 TB fall short here for lack of areal density; from 8 TB up, a standard IronWolf or WD Red Plus is the right call on the DS925+.
A worked configuration for the DS925+
Seagate IronWolf Pro or WD Red Plus in every bay is the recommendation for the DS925+. At 4 × 8 TB in SHR, the DS925+ lands 21.83 TiB usable, gives up 8 TB to parity, and survives 1 drive failing. Step the same 4 bays of the DS925+ up to 16 TB drives and it holds roughly twice that, at the CA$/TB the live table above shows.
SHR or RAID 6 in the DS925+?
With 4 bays the DS925+ gives a real choice. In SHR it keeps 21.83 TiB of the 4 × 8 TB and survives one failure; RAID 6 spends one more drive for two. The trade tips with large drives: after a failure the DS925+ must read every surviving drive in full to rebuild, which on 20 TB drives runs the better part of a day under peak load. So from 16 TB per drive up, RAID 6 is the calmer choice in the DS925+, and SHR-2 gives the same protection while still using mixed drive sizes.
One rule holds on every NAS, the DS925+ included: use CMR drives, not SMR. SMR drives rewrite overlapping tracks and collapse during a RAID rebuild, dragging a repair from hours into days.
The Synology drive policy on the DS925+
with a caveatPartly open, and this is the key news. On 16 April 2025 Synology announced that the 2025 Plus models would only create a storage pool with listed drives. With DSM 7.3 (version 7.3-81180, released 8 October 2025) Synology reversed that lock for hard drives and 2.5-inch SATA SSDs: Seagate IronWolf and WD Red Plus now install, initialize, pool and monitor normally. Only M.2 NVMe still requires a listed drive.
The DS925+ at a glance
| Bays | 4 × 3.5-inch SATA and 2.5-inch SATA SSD |
|---|---|
| Maximum raw capacity | 96 TB 4 × 24 TB, per the manufacturer |
| Processor | AMD Ryzen V1500B (4 cores, 8 threads) |
| Memory | 4 GB, DDR4 ECC SO-DIMM (2 slots) 32 GB official, ECC |
| M.2 NVMe | 2 slots 2 × M.2 NVMe. Note: for BOTH an NVMe cache and an NVMe storage pool, Synology still requires a drive from its own compatibility list. That is the remaining lock. |
| Network | 2 × 2.5GbE |
| Operating system | DSM 7.3 or newer |
| RAID types | SHR, SHR-2, Basic, JBOD, RAID 0, RAID 1, RAID 5, RAID 6, RAID 10 SHR also makes use of mixed drive sizes. |
Keep calculating
To see how much capacity is left after parity, the DS925+ capacity calculator is preset to its 4 bays and RAID types. For the DS925+, the wider basics of choosing a drive are in the buying guides, where we also explain why CMR rather than SMR is mandatory in any RAID array.
Frequently asked questions
What is the maximum storage in the DS925+?
4 drives, up to 96 TB raw per the manufacturer. 4 × 24 TB, per the manufacturer
How much of the DS925+ is actually usable?
In the DS925+, 4 × 8 TB in SHR yields about 21.83 TiB — that is 24 TB in drive-maker terms, with 8 TB to parity. It shows less than the label because it counts in powers of two.
Can I fit larger drives in the DS925+ later?
Yes, and with SHR it is easy: swap the DS925+'s drives for larger ones one at a time, and the gain arrives once the second-largest drive is also larger.
Can I put third-party drives in the DS925+?
Yes. Since DSM 7.3 (8 October 2025) the DS925+ accepts third-party hard drives and 2.5-inch SATA SSDs again — Seagate IronWolf, WD Red Plus and the like install and pool normally. Only M.2 NVMe still needs a drive from Synology's list.
Devin Chua works out which drives, RAM and NVMe cache fit which NAS model at nasdrives.ca, and what the RAID choice means for usable capacity, checked against what is in stock on Amazon.ca.
Data checked by Owen Nakamura, Technical editor (data checking)