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ZFS resliver performance improved!

January 6, 2010

I’m not being lucky with the Western Digital 1Tb disks in my home server.

That is to say I’m extremely pleased I have ZFS as both have now failed and in doing so corrupted data which ZFS has detected (although the users detected the problem first as the performance of the drive became so poor).One of the biggest irritations about replacing drives, apart from having to shut the system down as I don’t have hot swap hardware is waiting for the pool to resliver. Previously this has taken in excess of 24 hours to do.

However yesterday’s resilver was after I had upgraded to build 130 which has some improvements to the resilver code:


: pearson FSS 1 $; zpool status tank
  pool: tank
 state: ONLINE
status: The pool is formatted using an older on-disk format.  The pool can
        still be used, but some features are unavailable.
action: Upgrade the pool using 'zpool upgrade'.  Once this is done, the
        pool will no longer be accessible on older software versions.
 scrub: resilver completed after 6h28m with 0 errors on Wed Jan  6 02:04:17 2010

        NAME           STATE     READ WRITE CKSUM
        tank           ONLINE       0     0     0
          mirror-0     ONLINE       0     0     0
            c21t0d0s7  ONLINE       0     0     0
            c20t1d0s7  ONLINE       0     0     0
          mirror-1     ONLINE       0     0     0
            c21t1d0    ONLINE       0     0     0  225G resilvered
            c20t0d0    ONLINE       0     0     0

errors: No known data errors
: pearson FSS 2 $;

Only 6 ½ hours for 225G which while not close to the theoretical maximum is way better than 24 hours and the system was usable while this was going on.

From → Solaris

  1. ZFS’s 24 hours was WAY BETTER than the 3 or 4 days I was getting on a Macintosh with re-silvering of their mirroring of my 1.5TB external USB drives!

  2. That is one advantage of ZFS. It was only resilvering what had been written. So Although the drive is 1TB it only resilvers 225G. So had the disk been full it would have been up in the same range as your drive.
    Now however, if we assume it scales linearly it would complete in a little over 24 hours for a full 1TB.

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