RAID capacity calculator

Enter the drives you have — or the ones you are about to buy — and see how much space you actually get, how much goes to protection, and how many drives can fail before you lose data. Covers Synology SHR and SHR-2 as well as standard RAID, including arrays built from mixed drive sizes.

1 · Protection type

How the drives protect each other.

2 · Your drives

Mixed sizes are fine — that is exactly what SHR is for. Standard RAID levels can only use the smallest drive's capacity on every drive.

! RAID is not a backup. It survives a drive dying. It does not survive ransomware, a deleted folder, a fire or someone walking off with the box — every one of those reaches all the drives at once. You still need a second copy somewhere else, which is what the 3-2-1 rule is for.

Enclosures with enough bays

Based on the number of drives above.

Beyond the box

We size it, build it, and prove the restore works

Anyone can ship a NAS in a box. The reason our clients buy the hardware here is that the same team engineers it afterwards — sizing against how much your data actually changes, designing the RAID and volumes, building the backup, and testing a real restore before we hand it over.

Sizing before you spend

We work from your real data volume and change rate, not a bay count. Often the answer is a smaller unit with better drives — we will say so.

Installation & commissioning

DSM set up, RAID and volumes built, shares and permissions mapped to how your teams actually work, UPS shutdown tested.

Backup that is actually configured

Active Backup for servers, PCs and Microsoft 365, with off-site replication to a second site or to Synology C2 — not just a NAS with an empty schedule.

A restore test at handover

We restore something real and show you it worked. A backup nobody has ever restored from is a hope, not a plan.

Warranty handled here

A drive fails, you call us. We deal with the distributor and the RMA instead of handing you a serial number and a phone number.

Ongoing care, if you want it

Under a maintenance contract we monitor the array and the backup jobs, and run periodic restore drills — so a failure is a job ticket, not a discovery.

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Before you buy

Common questions

What is SHR, and should I use it?

Synology Hybrid RAID lets drives of different sizes work together without wasting the difference. With standard RAID 5, four drives of 8, 8, 4 and 4 TB are all treated as 4 TB and you get 12 TB. With SHR you get 16 TB. If every drive is the same size, SHR gives exactly the same result as RAID 5 — so the choice only matters when sizes differ, or when you plan to grow the array one drive at a time.

Why is my 8 TB drive only 7.28 TB?

Drive makers count a terabyte as 1,000,000,000,000 bytes; operating systems count 1,099,511,627,776. Nothing is missing — it is the same space described in two units. The "formatted" figure in the panel above is what your file manager will show.

How many drives can I lose?

RAID 1, RAID 5 and SHR survive one drive. RAID 6 and SHR-2 survive two. RAID 10 survives one drive from each mirrored pair — sometimes two in total, but not if both are in the same pair. RAID 0 and JBOD survive none: one drive fails and the array is gone.

Is RAID a backup?

No. RAID survives a drive dying. It does not survive ransomware, a deleted folder, a fire or theft, because every one of those reaches all the drives at once. RAID keeps you working through a hardware failure; a backup is what gets your data back. You need both.

Can I add drives later?

On Synology, yes. SHR and RAID 5/6 expand by adding a drive, or by replacing drives with larger ones one at a time, without rebuilding from scratch. Choose the bay count for where you want to end up, not where you start — going from a 2-bay to a 4-bay later means buying the enclosure twice.

Cross-check anything here against Synology's own RAID calculator. Not sure which model yet? The NAS buying guide asks five questions and names one. Ready to choose? See every Synology NAS we stock.

RAID capacity calculator

1 · Protection type

2 · Your drives

Enclosures with enough bays

We size it, build it, and prove the restore works

Common questions

Need pricing or stock? Talk to us.