A backup NAS is chosen on redundancy math, not software polish: bay count decides which RAID levels are available, RAID level decides how many drives can fail without loss, and the drives usually cost more than the chassis. This page selects on hardware and capacity facts only - bays, RAID capability, and which vendors document a named backup application - not on which platform is more pleasant to use.
Updated
Two bays in RAID 1 (a mirror) tolerate one drive failing, with usable capacity equal to one drive - the simplest redundant configuration and the floor for calling a NAS a backup target rather than a single point of failure. Four bays in RAID 5 also tolerate one drive failing, but usable capacity is three drives' worth instead of one - the same fault tolerance, more room. Six or more bays in RAID 6 tolerate two simultaneous failures, at the cost of two drives' capacity to parity.
None of this is a performance question. It is arithmetic: RAID 1 = 1 drive usable of n; RAID 5 = (n-1) drives usable; RAID 6 = (n-2) drives usable. The right answer for a backup target is whichever configuration matches how much downtime a rebuild can tolerate and how many drives you can afford to lose data across at once - not a brand preference.
Two vendors in our catalogue name a specific backup application on their own product pages, which is a feature-presence fact rather than a judgement of how well it works: Synology names Active Backup for Business as a DSM application, and QNAP names Hybrid Backup Sync (HBS 3) as a QTS application. We are not claiming either does the job better than the other - only that both vendors document a named application by that description, on their own sites, as of today.
Cheapest in-stock 2-bay (Synology DiskStation DS223 2-Bay Diskless, $237.14) plus two MDD 20TB drives at $499.99 each = $1237.12 for 20TB usable in a mirror.
Cheapest in-stock 4-bay (Synology DiskStation DS423 4-Bay Diskless, $360.62) plus four 20TB drives at $499.99 each = $2360.58 for 60TB usable in RAID 5 - three times the usable capacity of the mirror for roughly twice the total build cost.
Re-run either configuration at any capacity or RAID level in the NAS Builder.
RAID protects against a drive failing. It does not protect against a file being deleted, ransomware encrypting a share, or the enclosure itself failing - all three replicate identically to every drive in the array in real time. A NAS holding the only copy of anything irreplaceable is a bigger single point of failure than the drive it protects against, not a smaller one. The fix costs one more drive on a separate device, or a second NAS as a replication target - not a bigger array on the same box.
| Brand | Model | Bays | CPU | RAM | Network | Wty | Price | Buy |
|---|---|---|---|---|---|---|---|---|
| Synology | DiskStation DS223 2-Bay Diskless DSM 7 | 2 | Realtek RTD1619B (4-core) | 2GB DDR4 | 1GbE | 3yr | $237.14 | Buy โ |
| UGREEN | NASync DH2300 2-Bay UGOS Pro | 2 | โ | โ | 2.5GbE | 2yr | $239.99 | Buy โ |
| TerraMaster | F2-425 2-Bay TOS 6 | 2 | โ | โ | โ | 2yr | $254.99 | Buy โ |
| Synology | DiskStation DS423 4-Bay Diskless DSM 7 | 4 | Realtek RTD1619B (4-core) | 2GB DDR4 | 2x 1GbE | 3yr | $360.62 | Buy โ |
| Synology | DiskStation DS225+ 2-Bay DSM 7 | 2 | โ | โ | 2.5GbE | 3yr | $364.99 | Buy โ |
| TerraMaster | F4-425 4-Bay TOS 6 | 4 | โ | โ | โ | 2yr | $365.49 | Buy โ |
| UGREEN | NASync DXP2800 2-Bay UGOS Pro | 2 | Intel N100 (4-core) | 8GB DDR5 | 2.5GbE | 2yr | $369.99 | Buy โ |
| QNAP | TS-464-8G 4-Bay QTS 5 | 4 | Intel Celeron N5105 (4-core) | 8GB DDR4 | 2x 2.5GbE | 2yr | $599.92 | Buy โ |
| Synology | DiskStation DS425+ 4-Bay Diskless DSM 7 | 4 | โ | โ | 2.5GbE | 3yr | $599.99 | Buy โ |
| UGREEN | NASync DXP4800 Plus 4-Bay UGOS Pro | 4 | Intel Pentium Gold 8505 (5-core) | 8GB DDR5 | 10GbE + 2.5GbE | 2yr | $619.99 | Buy โ |
| TerraMaster | F4-425 Plus 4-Bay TOS 6 | 4 | Intel N150 (4-core) | โ | โ | 2yr | $649.99 | Buy โ |
| Synology | DiskStation DS925+ 4-Bay DSM 7 | 4 | AMD Ryzen V1500B (4-core) | 4GB DDR4 ECC | 2x 2.5GbE | 3yr | $674.00 | Buy โ |
| Asustor | Lockerstor 4 Gen2+ AS6704T 4-Bay ADM | 4 | Intel quad-core | 4GB DDR4 | 2x 5GbE | 3yr | $681.99 | Buy โ |
| UniFi | UNAS Pro 4 4-Bay UniFi Drive | 4 | โ | โ | โ | โ | $699.00 | Buy โ |
| QNAP | TS-664-8G 6-Bay QTS 5 | 6 | Intel Celeron N5105 (4-core) | 8GB DDR4 | 2x 2.5GbE | 2yr | $743.07 | Buy โ |
| UGREEN | NASync DXP4800 Pro 4-Bay UGOS Pro | 4 | โ | โ | โ | 2yr | $799.99 | Buy โ |
| UGREEN | NASync DXP6800 Plus 6-Bay UGOS Pro | 6 | Intel Core i3-1215U (6-core) | โ | โ | 2yr | $886.96 | Buy โ |
| UGREEN | NASync DXP6800 Pro 6-Bay UGOS Pro | 6 | Intel Core i5-1235U (10-core) | 8GB DDR5 | 2x 10GbE | 2yr | $1,013.91 | Buy โ |
| Asustor | Flashstor 6 Gen2 FS6806X All-Flash ADM | 6 | โ | โ | 10GbE | 3yr | $1,040.99 | Buy โ |
| Synology | DiskStation DS1525+ 5-Bay DSM 7 | 5 | AMD Ryzen V1500B (4-core) | 8GB DDR4 ECC | 2x 2.5GbE | 3yr | $1,309.99 | Buy โ |
| Synology | DiskStation DS1825+ 8-Bay DSM 7 | 8 | AMD Ryzen V1500B (4-core) | 8GB DDR4 ECC | 2x 2.5GbE | 3yr | $1,367.99 | Buy โ |
| Asustor | Lockerstor 6 Gen3 AS6806T 6-Bay ADM | 6 | AMD Ryzen quad-core 3.8GHz | 16GB DDR5 ECC | 10GbE | 3yr | $1,680.99 | Buy โ |
| QNAP | TS-233 2-Bay Desktop NAS Diskless QTS 5 | 2 | ARM Cortex-A55 (4-core) | 2GB | 1GbE | 3yr | Out of stock | Check availability |
| TerraMaster | F4-424 Pro 4-Bay TOS 6 | 4 | Intel Core i3-N305 (8-core) | 32GB DDR5 | 2x 2.5GbE | 2yr | Out of stock | Check availability |
| UGREEN | NASync DXP8800 Plus 8-Bay UGOS Pro | 8 | Intel Core i5-1235U (10-core) | 8GB DDR5 | 2x 10GbE | 2yr | Out of stock | Check availability |
Every 2-bay NAS ยท Every 4-bay NAS ยท RAID usable-capacity planner ยท NAS hard drives, live $/TB ยท UPS for a NAS.
Two, for a mirror that survives one drive failing - the smallest configuration with any redundancy at all. Four bays in RAID 5 add usable capacity (three drives' worth instead of one) for the same one-drive fault tolerance, which matters once the backup set outgrows a single drive's capacity.
No. RAID protects against a drive failing; it does not protect against deletion, ransomware, or the enclosure itself failing, all of which replicate to every drive in the array identically. A NAS holding a household's ONLY backup copy is itself a single point of failure - a second copy on a different device or medium is what makes it an actual backup rather than a second copy of the same risk.
Synology names Active Backup for Business on its own site as a DSM application; QNAP names Hybrid Backup Sync (HBS 3) on its own site as a QTS application. Both are vendor-documented software features, not a claim we are making about how well either performs.
Whatever the bay count supports: RAID 1 (mirror) at 2 bays, RAID 5 at 4+ bays for one-drive tolerance with more usable space, RAID 6 at 6+ bays for two-drive tolerance. The right choice depends on bay count and how much downtime a rebuild can tolerate, not on which brand is running it.
A 2-bay mirror: $1237.12 for the chassis plus two 20TB drives, 20TB usable. A 4-bay RAID 5: $2360.58 for the chassis plus four 20TB drives, 60TB usable. Both computed from today's live catalogue.
CMR (or ePMR). A shingled (SMR) drive rebuilding a degraded array is the single most repeated warning in this category - rebuilds that should take a day have taken over a week on SMR drives, exactly when the array has no spare redundancy left. See the NAS drive tracker's recording-technology column before buying.