An encoding system and associated method protect against miscorrection due to
parity sector correction in, for example, an on-drive RAID system. The system adds
a parity cluster block, which itself is a complete, C3-protected cluster. Having
the cluster level, C4 level correction, by parity sectors, checked and verified
by C3 checks that have high reliability level, as well as the capability for checking
consistency of a cluster block, even in the presence of "jami" errors, makes this
possibility unlikely. A scrub algorithm avoids read-modify-write operations by
deferring the completion of the C2 and C3-ckecks until the storage device is idle.
