WD Ultrastar DC HC570 - 3.5" Enterprise HDD - 22TB SATA SED

The Ultrastar DC HC570 is a 22TB enterprise hard drive and WD's 8th-generation HelioSeal platform. It moved to a 10-disk design with 2nd-generation OptiNAND and introduced ArmorCache, which uses the embedded iNAND flash to protect in-flight write data during unexpected power loss.

Enterprise Specs

7,200 RPM, 512MB cache, ePMR with CMR, available in SATA 6Gb/s and SAS 12Gb/s. Workload rating is 550TB/year with a 2.5 million hour MTBF and 5-year warranty. Helium-sealed. Available in both 4Kn and 512e sector formats.

Sustained transfer rate is 291 MB/s. Idle power is 5.7W on SATA, giving a power efficiency of 0.26 W/TB, a noticeable improvement over the HC560's 0.31 W/TB.

ArmorCache

ArmorCache extends the OptiNAND flash chip's role beyond metadata storage. During normal operation, the drive uses write caching for performance (writing to DRAM first, then flushing to platters). If power is lost before the flush completes, ArmorCache redirects the in-flight data from DRAM to the embedded flash, which retains data without power. On the next power-up, the drive replays the cached writes to the platters. This reduces the window for data loss during ungraceful shutdowns without requiring the performance penalty of disabling write caching.

Drive Security Variants

The last character of the model number indicates the security mode:

• SE (Base) -- No encryption, sanitize overwrite only. Available on both SATA and SAS. SATA models include ATA Security Feature Set as standard.
• SED (Self-Encrypting Drive) -- Hardware AES-256 encryption with TCG Enterprise protocol. Available on both SATA and SAS.

ISE and SED-FIPS variants were offered on earlier Ultrastar generations (HC520-HC550) but are not available on the HC560 and later.

Homelab Relevance

The HC570 is starting to appear on the used market as early deployments hit their refresh cycle. At 22TB per drive, it offers strong density for homelabbers building high-capacity pools. The improved power efficiency (0.26 W/TB vs 0.31 for the HC550/HC560) adds up across a multi-drive NAS.

Best for: High-density NAS builds where 22TB per slot minimizes the number of drives needed and used pricing has come down from new-retail levels.

Avoid if: Used HC550 18TB drives are significantly cheaper per TB in your market. The older platform is still reliable and the price difference may outweigh the density gain.