On Dec 20, 2010, at 4:19 PM, Edward Ned Harvey <opensolarisisdeadlongliveopensola...@nedharvey.com> wrote:
>> From: Erik Trimble [mailto:erik.trim...@oracle.com] >> >> We can either (a) change how ZFS does resilvering or (b) repack the >> zpool layouts to avoid the problem in the first place. >> >> In case (a), my vote would be to seriously increase the number of >> in-flight resilver slabs, AND allow for out-of-time-order slab >> resilvering. > > Question for any clueful person: > > Suppose you have a mirror to resilver, made of disk1 and disk2, where disk2 > failed and is resilvering. If you have an algorithm to create a list of all > the used blocks of disk1 in disk order, then you're able to resilver the > mirror extremely fast, because all the reads will be sequential in nature, > plus you get to skip past all the unused space. Sounds like the definition of random access :-) > > Now suppose you have a raidz with 3 disks (disk1, disk2, disk3, where disk3 > is resilvering). You find some way of ordering all the used blocks of > disk1... Which means disk1 will be able to read in optimal order and speed. Sounds like prefetching :-) > Does that necessarily imply disk2 will also work well? Does the on-disk > order of blocks of disk1 necessarily match the order of blocks on disk2? This is an interesting question, that will become more interesting as the physical sector size gets bigger... -- richard > _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
