Vendor neutral storage math
Every RAID calculator on the internet belongs to a hardware vendor, so each one models exactly one scheme. Synology's models SHR. TrueNAS-flavoured tools model RAIDZ. Controller vendors model the classic levels. No manufacturer tool compares all three for the same physical drives, which is the one comparison you need with a shopping cart open.
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| Layout | Usable | As reported | Survives |
|---|---|---|---|
| Synology SHR | 48 TB | 43.66 TiB | 1 drive |
| Synology SHR-2 | 32 TB | 29.1 TiB | 2 drives |
| ZFS RAIDZ1 | 48 TB | 43.66 TiB | 1 drive |
| ZFS RAIDZ2 | 32 TB | 29.1 TiB | 2 drives |
| RAID 5 | 48 TB | 43.66 TiB | 1 drive |
| RAID 6 | 32 TB | 29.1 TiB | 2 drives |
| RAID 10 | 32 TB | 29.1 TiB | 1 drive |
Now make them mismatched. Drives of 4, 8, 8 and 12 TB give 12 TB under RAID 5 and 20 TB under Synology SHR, a gap of 8 TB. Standard RAID and every ZFS vdev truncate each member to the smallest drive and strand the rest.
DSM is still the most approachable NAS operating system, and two bays in SHR gives you one drive of redundancy without buying four drives on day one. Hardware transcoding is included.
Best for: A first NAS for photos, file sync and a modest media library.
Check priceECC memory, four M.2 slots and a 10GbE port. The specification is genuinely enthusiast grade, and so is the price.
Best for: People who already know they are network-limited and have the switch to match.
Check priceUGREEN pairs an Intel N100 with M.2 slots, so it handles Plex transcoding and container workloads that a low-cost ARM box cannot.
Best for: People who want budget hardware but expect to run more than a file share on it.
Check price900 W of capacity is far more than a home NAS needs. You are buying runtime and a replaceable battery pack, not wattage.
Best for: A rack with several devices, or anyone who wants to ride out short outages entirely.
Check priceThe N100 idles in single-digit watts and still has Quick Sync for transcoding. For a always-on box, idle draw matters more than peak performance.
Best for: Home Assistant, Pi-hole, a few containers and light Plex duty.
Check price2.5GbE roughly triples real transfer speed over gigabit and costs very little now. It is the single best value upgrade in a home lab.
Best for: Connecting a NAS with a 2.5GbE port to one or two desktops.
Check priceBudgets are ranges; check the current price on Amazon. As an Amazon Associate we earn from qualifying purchases.
An eight-bay NAS is a big purchase on its own. The eight drives that go in it are $200 to $500 each, so $2,000 to $4,000 in a single order. And unlike the box, drives fail and get upgraded, so that spend repeats every few years.
Which is why the drive pages here get the same care as the calculators. Two requirements are not negotiable: CMR recording, never SMR, because shingled drives can take days to rebuild an array, and a published NAS workload rating of at least 180 TB per year.
| Build | Enclosure budget | Drives budget | Drive share |
|---|---|---|---|
| 2 bay, 8 TB drives | Under $500 | Under $750 | 66% |
| 4 bay, 8 TB drives | Under $1,000 | Under $1,500 | 66% |
| 4 bay, 20 TB drives | Under $1,000 | Under $3,500 | 82% |
| 8 bay, 16 TB drives | Under $2,500 | Under $5,000 | 77% |
| 8 bay, 20 TB drives | Under $2,500 | Under $7,500 | 83% |
Budgets are rounded up from the catalog prices on our comparison pages. Prices change often, so check the current one on Amazon. As an Amazon Associate we earn from qualifying purchases.
All hardware guides · Specs for 48 NAS models · Reference charts · Head to head comparisons · Guides
Nothing is missing and nobody cheated you. Drive makers sell decimal terabytes, where one TB is exactly 1,000,000,000,000 bytes. Your operating system reports binary tebibytes, where one TiB is 2 to the power of 40 bytes, or 1,099,511,627,776. Divide one by the other and you get 0.909495, so a 20 TB drive genuinely holds 18.19 TiB of the same bytes.
The practical effect is a fixed 9.05 percent apparent shrink at every capacity, before any filesystem overhead. Windows and most NAS interfaces simply label a tebibyte with the letters "TB". On top of that, ext4 and Btrfs reserve roughly one to two percent for metadata, and ZFS reserves 1/64 of the pool as slop space. Those are real, and they are much smaller than the unit difference.
The full conversion chart covers every capacity from 1 TB to 100 TB, and the RAID calculator shows both units side by side for whatever drives you own.
RAID is not a backup. It protects against a drive dying. It does nothing about accidental deletion, ransomware, a controller writing garbage to every member, theft, fire or flood, because every one of those reaches all drives at once. Size three copies with the 3-2-1 backup calculator and keep one of them off site.
