Synology SHR Explained: Mixing Drive Sizes Without Wasting Space
Compatibility data on this site last refreshed 2026-10-29 · reading time ~3 min
SHR is Synology's automated RAID layout. It gives you RAID-1/5/6-class redundancy but packs mixed-capacity drives more efficiently than classic RAID, which always caps every disk at the smallest one in the array.
A quick example
Four drives of 4, 4, 8 and 12TB: classic RAID 5 (odd parity aside) uses 4TB from each disk. SHR instead pairs the two 4TB drives in mirror and stripes the remaining 8+12TB with parity — roughly 17TB usable instead of 12TB, with the same one-drive failure tolerance.
When to use classic RAID instead
- You may migrate the array to another brand's NAS later — SHR is Synology-only; classic RAID layouts travel better
- All your drives are the same size anyway — SHR's advantage disappears
- You want to grow the array one disk at a time in a strictly predictable way
Things people get wrong
SHR still needs redundancy headroom: two-disk-failure tolerance (SHR-2) is wise for arrays above ~40TB or during risky operations. And mixing drive brands is fine mechanically, but array performance follows the slowest and smallest drive in each stripe.
Quick answers
Can I add a bigger drive to an SHR volume later?
Yes — SHR will use the extra capacity. With classic RAID 5 the same upgrade wastes the difference until every disk is replaced.
Is SHR slower than RAID 5?
Marginally at most; both do similar work. Real-world throughput is dominated by the drives and the network.
Check your exact model
Compatibility is per machine and per part number. Pick your model for its full official drive list: