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WD Ultrastar HC530 vs HC550 vs HC570
Buy the HC530 for the lowest cost per terabyte and the HC550 for 18 TB per bay on a mature platform; at matching capacity they are interchangeable in an array. The HC570 reaches 22 TB with OptiNAND but is newer, scarcer used and costs more per terabyte. All three are 7200 rpm helium CMR drives.
Updated Nov 3, 2026
Side by side
| Specification | DC HC530 | DC HC550 | DC HC570 |
|---|---|---|---|
| Capacities | 14 TB | 16, 18 TB | 22 TB |
| Platters | 8 | 9 | 10 |
| Recording | CMR | CMR, energy-assisted | CMR, energy-assisted, OptiNAND |
| Spindle speed | 7200 rpm | 7200 rpm | 7200 rpm |
| Cache | 512 MB | 512 MB | 512 MB |
| Fill | Helium | Helium | Helium |
| Interfaces | SATA 6 Gb/s, SAS 12 Gb/s | SATA 6 Gb/s, SAS 12 Gb/s | SATA 6 Gb/s, SAS 12 Gb/s |
| Sector formats | 512e, 4Kn | 512e, 4Kn | 512e, 4Kn |
| Max sustained transfer | About 265 MB/s | About 270 MB/s | About 290 MB/s |
| Workload rating | 550 TB/year | 550 TB/year | 550 TB/year |
| MTBF | 2.5 million hours | 2.5 million hours | 2.5 million hours |
| Original warranty | 5 years | 5 years | 5 years |
| Common used part numbers | WUH721414AL5204 (SAS, 512e) | WUH721818AL4200 (SAS, 4Kn), WUH721818AL5204 (SAS, 512e) | WUH722222ALE6L4 (SATA, 512e) |
- Transfer rates are datasheet maximums for the top capacity in each family, on the outer tracks.
- In WD part numbers, AL means SAS and ALE means SATA; 5204 is 512e SAS, 4200 is 4Kn SAS and E6L4 is 512e SATA.
Which to pick
RAIDZ2 pool where bays are not the limit
HC530 14TB
Lowest cost per terabyte of the three, and a common SAS datacenter pull.
Most homelab and small-business builds
HC550 18TB
18 TB per bay on a platform that has shipped in volume for years. The 4Kn SAS version is often the cheapest route to 18 TB.
Few bays, or consolidating many small drives
HC570 22TB
The most capacity per bay. Expect a higher cost per terabyte and longer resilvers.
Older RAID controller or legacy boot firmware
512e version of any generation
Some older controllers and USB enclosures cannot use 4Kn sectors.
Our test data and stock
Every unit of these models we have tested in-house, from our test database, and what is listed today.
Ultrastar DC HC530 14TB SAS
WUH721414AL5204
Currently sold out, 18 units tested since Jun 2026
- Units tested
- 18
- Passed
- 18
- Median hours
- 25,170 h
Ultrastar DC HC550 18TB SAS 4Kn
WUH721818AL4200
14 in stock from $465.46
- Units tested
- 19
- Passed
- 19
- Median hours
- 12,784 h
- Price
- $465.46
Ultrastar DC HC550 18TB SAS 512e
WUH721818AL5204
Currently sold out, 4 units tested since Jun 2026
- Units tested
- 4
- Passed
- 0
WD Gold 18TB SATA (HC550 platform)
WD181KRYZ
2 in stock from $465.46
- Units tested
- 3
- Passed
- 3
- Median hours
- 48,415 h
- Price
- $465.46
Ultrastar DC HC570 22TB
We have not tested this model yet. Ask for a quote and we will source it.
Common questions
Can HC530 and HC550 drives share a pool?+
In separate vdevs, yes. Inside one vdev the capacities must match, and the HC550 was never sold at 14 TB, so pair HC530s with other 14 TB drives.
Do 4Kn SAS Ultrastars work in a NAS?+
Yes, on a current HBA in IT mode with Linux, FreeBSD, TrueNAS or current Windows. Older RAID controllers and some USB enclosures do not support 4Kn; buy 512e for those.
Is energy-assisted recording a reliability risk?+
No published evidence says so. WD gives the HC550 the same workload, MTBF and warranty ratings as the HC530, and it has shipped in volume for years.
Is the WD Gold 18TB an HC550?+
The WD Gold 18TB (WD181KRYZ) is built on the HC550 platform and sold under the Gold name as a SATA drive, which is why it sits with the HC550 on this page.