Repaired blocks indicate that ZFS found mismatched checksums and corrected the underlying data. A small number of repaired blocks is normal for large storage pools, and occasional bit rot is expected. A rising number of repaired blocks over multiple scrubs signals a problem. //

• Occasional repaired blocks are normal in large pools but, rising totals across scrubs indicate degrading hardware.
• The READ and WRITE counters indicate device level I/O errors. Persistent values on a single device suggest cable problems, controller instability, or a failing disk.
• The CKSUM column indicates checksum mismatches detected during normal reads.