Kevin wrote: > After a scrub of a pool with 3 raidz2 vdevs (each with 5 disks in them) I see > the following status output. Notice that the raidz2 vdev has 2 checksum > errors, but only one disk inside the raidz2 vdev has a checksum error. How is > this possible? I thought that you would have to have 3 errors in the same > 'stripe' within a raidz2 vdev in order for the error to become unrecoverable.
A checksum error on a disk indicates that we know for sure that this disk gave us wrong data. With raidz[2], if we are unable to reconstruct the block successfully but no disk admitted that it failed, then we have no way of knowing which disk(s) are actually incorrect. So the errors on the raidz2 vdev indeed indicate that at least 3 disks below it gave the wrong data for a those 2 blocks; we just couldn't tell which 3+ disks they were. It's as if I know that A+B==3, but A is 1 and B is 3. I can't tell if A is wrong or B is wrong (or both!). The checksum errors on the cXtXdX vdevs didn't result in data loss, because we reconstructed the data from the other disks in the raidz group. --matt _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
