DSM policy allows third-party SATA HDDs; verify exact MPN
DS223 + 2 × 4TB IronWolf
A checked starting combination targeting about 4TB usable with shr / raid 1-style single-drive redundancy.
Lowest checked total$543.17Amazon + Amazon
Lowest one-store total$543.17Amazon
Approx. usable4TB
Checked value$135.79/TB
What the bundle contains
Capacity and redundancy
The mirror can continue after one drive fails; RAID is not a backup.
Approximation: $(2 - 1) × 4TB = 4TB$. Filesystem formatting, system partitions, snapshots, and RAID implementation reduce displayed free space.