Experiments / live

RAIDZ1 reconstruction

One stripe across four data disks and a single parity disk. The parity column is nothing but the running XOR of the data: P = D₀ ⊕ D₁ ⊕ D₂ ⊕ D₃. Click a disk to fail it, and — because ZFS's checksums tell it which disk lied — watch the missing bytes reappear as the XOR of the survivors. Then fail a second disk and see the single equation run out of room. The algebra, and why it only works when the location is known, is in the essay.