2012-03-21 17:28, Edward Ned Harvey wrote:
From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
boun...@opensolaris.org] On Behalf Of MLR
...
Am I correct in thinking this means, for example, I have a single
>> 14 disk raidz2 vdev zpool,


It's not advisable to put more than ~8 disks in a single vdev, because it
really hurts during resilver time.  Maybe a week or two to resilver like
that.

Yes, that's important to note also. While ZFS marketing initially
stressed that unlike traditional RAID systems, a "rebuild" of ZFS
onto a spare/replacement disk only needs to copy referenced data
and not the whole disk, it somehow fell off the picture that such
rebuild is a lot of random IO - because the data block tree must
be read in as a tree walk, often with emphasis on block "age" (its
birth TXG number). If your pool is reasonably full (and who runs
it empty?) then this is indeed lots of random IO, and a blind
full-disk copy would have gone orders of magnitude faster.
The less disk participate in this thrashing - the faster it will
go (less data needed overall to reconstruct a disk's worth of
sectors from redundancy data).

That's the way I understand the problem, anyway...

//Jim
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