How much storage fits in the Synology DiskStation DS923+?
By Devin Chua · Data checked by Owen Nakamura · Updated · Prices checked The Synology DiskStation DS923+ takes 4 drives, up to 96 TB raw, but usable is the number that matters: 4 × 8 TB in SHR gives 21.83 TiB for about CA$2,288 in drives, 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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Want to know whether the DS923+ fits your actual storage plan? Open the NAS Builder with this model weighted.
Usable space in the DS923+, by drive size
All 4 bays filled with equal drives in SHR, the DS923+’s sensible default. Usable TiB is what the NAS reports; TB is the drive maker’s unit.
| Drive size | Raw | Usable (TB) | Usable (TiB) | Drive failures survived |
|---|---|---|---|---|
| 4 × 4 TB | 16 TB | 12 TB | 10.91 TiB | 1 |
| 4 × 8 TB | 32 TB | 24 TB | 21.83 TiB | 1 |
| 4 × 12 TB | 48 TB | 36 TB | 32.74 TiB | 1 |
| 4 × 16 TB | 64 TB | 48 TB | 43.66 TiB | 1 |
| 4 × 20 TB | 80 TB | 60 TB | 54.57 TiB | 1 |
| 4 × 24 TB | 96 TB | 72 TB | 65.48 TiB | 1 |
How much space you actually need
Start from what you store today, not from the drive sizes. As rough guides: a 24-megapixel RAW photo is about 25 to 30 MB, a phone photo 3 to 5 MB, and an hour of 4K phone video around 20 GB; check a folder of your own files for real numbers. Add the growth you expect over the next three to five years, then keep about 20 percent free so the pool does not run full.
Then plan the backup copy. RAID keeps the DS923+ running through a drive failure; it does not protect against deletion, ransomware, theft or fire. Size a second copy (an external drive, a second NAS or a cloud plan) for the data you cannot replace, which is often far less than the array.
For your own mix of drive sizes and RAID types, use the DS923+ capacity calculator. For drives that fit and their current Amazon.ca prices, see the best drives for the DS923+.
A worked configuration for the DS923+
WD Red Pro or Seagate IronWolf Pro in every bay is the recommendation for the DS923+. At 4 × 8 TB in SHR, the DS923+ lands 21.83 TiB usable for about CA$2,288 in drives, gives up 8 TB to parity, and survives 1 drive failing. Step the same 4 bays of the DS923+ up to 16 TB drives and it holds roughly twice that, at the CA$/TB the live table above shows.
SHR or RAID 6 in the DS923+?
With 4 bays the DS923+ 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 DS923+ 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 DS923+, and SHR-2 gives the same protection while still using mixed drive sizes.
One rule holds on every NAS, the DS923+ included: use CMR drives, not SMR. SMR drives rewrite overlapping tracks and collapse during a RAID rebuild, dragging a repair from hours into days.
Drive policy: Synology's 2025 drive policy applies only to models launched from 2025, so the DS923+ takes third-party hard drives and 2.5-inch SATA SSDs as it always has. The DS923+’s full compatibility rules.
Keep calculating
To see how much capacity is left after parity, the DS923+ capacity calculator is preset to its 4 bays and RAID types. For the DS923+, the wider basics of choosing a drive are in the buying guides, and CMR versus SMR explains why SMR drives do not belong in a RAID array. Wondering what the DS923+ can actually do: Plex, Immich, Docker, VMs? See what the DS923+ can run.
Frequently asked questions
What is the maximum storage in the DS923+?
4 drives, up to 96 TB raw per the manufacturer. 4 × 24 TB: the largest drive on Synology's compatibility list for this model. With a DX517 expansion the figure rises accordingly.
How much of the DS923+ is actually usable?
In the DS923+, 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 DS923+ later?
Yes, and with SHR it is easy: swap the DS923+'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 DS923+?
Yes. Synology's 2025 drive policy applies only to models launched from 2025, so the DS923+ takes third-party hard drives and 2.5-inch SATA SSDs as it always has.
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)