> > Ah, that's a major misconception on my part then. I'd thought I'd read > > that unlike any other RAID implementation, ZFS checked and verified > > parity on normal data access.
> That would be useless, and not provide anything extra. I think it's useless if a (disk) block of data holding RAIDZ parity never has silent corruption, or if scrubbing was a lightweight operation that could be run often. > ZFS will do a > block checksum check (that is, for each block read, read the checksum > for that block, and compare to see if it is OK). If the block checksums > show OK, then reading the parity for the corresponding data yields no > additional useful information. It would yield useful information about the status of the parity information on disk. The read would be done because you're already paying the penalty for reading all the data blocks, so you can verify the stability of the parity information on disk by reading an additional amount. > I'm assuming that in a RAIDZ, RAIDZ2, or mirror configuration, should a > block checksum show the corresponding block is corrupted, then ZFS will > read the parity (or corresponding mirror) block, and attempt to > re-construct the "bad" block, give the corrected info to the calling > process, then re-writing the corrected data to a new block section on > the disk(s). > > Right? I was assuming that *all* the data for a FS block was read and if redundant, the redundancy was verified correct (same data on mirrors, valid parity for RAIDZ) or the redundacy would be repaired. At least with a mirror I have a chance of reading all copies over time. With RAIDZ, I'll never read the parity until a problem or a scrub occurs. Nothing wrong with that. I had simply managed to convince myself that it did more. -- Darren Dunham [EMAIL PROTECTED] Senior Technical Consultant TAOS http://www.taos.com/ Got some Dr Pepper? San Francisco, CA bay area < This line left intentionally blank to confuse you. > _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
