On Mon, Aug 1, 2011 at 2:16 PM, Neil Perrin <neil.per...@oracle.com> wrote:
> In general the blogs conclusion is correct . When file systems get full
> there is
> fragmentation (happens to all file systems) and for ZFS the pool uses gang
> blocks of smaller blocks when there are insufficient large blocks.

The blog doesn't mention how full the pool was. It's pretty well
documented that performance takes a nosedive at a certain point.

A slow scrub is actually not related to the problems in the blog post,
since there's not a lot of writes during (or at least caused by) a
scrub. Fragmentation is a real issue with pools that are (or have
been) very full. The data gets written out in fragments and has to be
read back in the same order.

If the mythical bp_rewrite code ever shows up, it will be possible to
defrag a pool. But not yet.

-B

-- 
Brandon High : bh...@freaks.com
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