How much storage fits in the Synology DiskStation DS423+?
By Devin Chua · Data checked by Owen Nakamura · Updated The Synology DiskStation DS423+ 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 DS423+, by price per TB
Only families with confirmed CMR recording and a 24/7 rating, in stock on Amazon.ca and sized for the DS423+. SMR drives are deliberately kept out.
What sets the DS423+ apart
The price entry with four bays and SHR. The Celeron J4125 can transcode Plex with hardware acceleration, but the 2 GB of RAM out of the box is tight: the single free SO-DIMM is effectively mandatory and caps you at 6 GB.
Who the DS423+ is for
The DS423+'s Intel Celeron J4125 (4 cores) is the home-NAS sweet spot. Its integrated graphics hardware-transcode Plex — 4K HEVC included, through Intel Quick Sync — and it runs a stack of Docker containers without complaint; heavy virtualization is the one thing it leaves to bigger machines. With 2 GB stock and up to 6 GB, the DS423+ suits a household that wants its media server and its drives in one quiet box.
How the DS423+'s network shapes the drive choice
The DS423+ connects over 2 × 1GbE, and that ceiling decides everything below it. A gigabit link tops out near 110 MB/s, which even a single 5400 rpm NAS drive clears easily. So on the DS423+ a faster, pricier Pro drive returns no extra throughput at all: put an IronWolf or WD Red Plus in every bay and buy on CA$/TB, warranty and noise. The only reason to pay for a Pro drive on the DS423+ is its longer warranty, not speed.
A worked configuration for the DS423+
Seagate IronWolf Pro or WD Red Plus in every bay is the recommendation for the DS423+. At 4 × 8 TB in SHR, the DS423+ lands 21.83 TiB usable, gives up 8 TB to parity, and survives 1 drive failing. Step the same 4 bays of the DS423+ up to 16 TB drives and it holds roughly twice that, at the CA$/TB the live table above shows.
SHR or RAID 6 in the DS423+?
With 4 bays the DS423+ 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 DS423+ 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 DS423+, and SHR-2 gives the same protection while still using mixed drive sizes.
One rule holds on every NAS, the DS423+ 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 DS423+
unrestrictedOpen. The 2025 restriction does not apply retroactively; every NAS drive works.
The DS423+ at a glance
| Bays | 4 × 3.5-inch SATA and 2.5-inch SATA SSD |
|---|---|
| Maximum raw capacity | 96 TB 4 × 24 TB: the largest drive on Synology's list for this model. The often-quoted 108 TB is the maximum volume size, not the sum of drives. |
| Processor | Intel Celeron J4125 (4 cores) |
| Memory | 2 GB, DDR4 SO-DIMM, no ECC (2 GB soldered plus 1 slot) 6 GB official (2 GB fixed plus a 4 GB module). In practice a 16 GB module runs (giving 18 GB); Synology does not endorse it. |
| M.2 NVMe | 2 slots 2 × M.2 NVMe for cache; an NVMe storage pool requires a Synology drive |
| Network | 2 × 1GbE |
| Operating system | DSM 7.x |
| 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 DS423+ capacity calculator is preset to its 4 bays and RAID types. For the DS423+, 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 DS423+?
4 drives, up to 96 TB raw per the manufacturer. 4 × 24 TB: the largest drive on Synology's list for this model. The often-quoted 108 TB is the maximum volume size, not the sum of drives.
How much of the DS423+ is actually usable?
In the DS423+, 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 DS423+ later?
Yes, and with SHR it is easy: swap the DS423+'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 DS423+?
Yes, without restriction. The 2025 Synology drive lock covers only the 2025 models, so the DS423+ takes any NAS drive and has always done so.
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)