Western Digital 640GB
Desktop HDD
Part number WD6400AAKS · 3.5" SATA HDD. If your machine is listed below, this drive is officially supported — not a forum workaround.
Check WD6400AAKS price on Amazon partner link
No series-level recording rating is on file for this part number yet — check the exact model for CMR vs SMR before buying it as a large cold copy (SMR is the one trait that makes a 16 TB+ backup copy painfully slow). The 3-2-1 guide and the backup tools encyclopedia cover what to schedule it with.
Compatibility verdict
It appears on the official compatibility lists of 146 machines and series — 66 Synology, 80 QNAP. Check the class badge above: drives tagged NAS or Enterprise are built for 24/7 multi-bay operation. Desktop-class drives often lack vibration resistance and are usually absent from vendor HCLs. No series-level recording rating is on file for this part number yet, so check CMR vs SMR on the exact model before buying for an array.
Compatible NAS models
Same-capacity alternatives
Other drives listed at 640 GB capacity, ranked by how many machines list them:
Quick answers
Is the WD6400AAKS officially compatible with my NAS?
It appears on the official compatibility lists of 146 machines and series — 66 Synology, 80 QNAP. Every machine page linked below shows the vendor's own list entry, refreshed daily.
Is the WD6400AAKS a good NAS drive?
Check the class badge above: drives tagged NAS or Enterprise are built for 24/7 multi-bay operation. Desktop-class drives often lack vibration resistance and are usually absent from vendor HCLs. No series-level recording rating is on file for this part number yet, so check CMR vs SMR on the exact model before buying for an array.
Can I use the WD6400AAKS for a 3-2-1 cold backup copy?
No series-level recording rating is on file for this part number yet — check the exact model for CMR vs SMR before buying it as a large cold copy (SMR is the one trait that makes a 16 TB+ backup copy painfully slow). The 3-2-1 guide and the backup tools encyclopedia cover what to schedule it with.
What are alternatives to the WD6400AAKS?
At the same capacity, the most widely listed alternatives are Western Digital WD6401AALS (72 machines), Western Digital WD6402AAEX (72 machines), Seagate ST3640323AS (72 machines). The full ranked list is below.