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Date: Thu, 17 Jan 2013 10:32:59 +0100
From: Nicolas Rachinsky <fbsd-mas-0@ml.turing-complete.org>
To: Andriy Gapon <avg@FreeBSD.org>
Subject: Re: slowdown of zfs (tx->tx)
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* Andriy Gapon <avg@FreeBSD.org> [2013-01-16 14:05 +0200]:
> on 16/01/2013 12:14 Steven Hartland said the following:
> > You only have ~11% free so yer it is pretty full ;-)
> 
> just in case, Steve is not kidding.
> 
> Those free hundreds of gigabytes could be spread over the terabytes and could be
> quite fragmented if the pool has a history of adding and removing lots of files.
>  ZFS could be spending quite a lot of time in that case when it looks for some
> free space and tries to minimize further fragmentation.
> 
> Empirical/anecdotal safe limit on pool utilization is said to be about 70-80%.
> 
> You can test if this guess is true by doing the following:
> kgdb -w
> (kgdb) set metaslab_min_alloc_size=4096
> 
> If performance noticeably improves after that, then this is your problem indeed.

I tried this, but I didn't notice any difference in performance.

Next I'll try the update Artem suggested.

Thanks

Nicolas
-- 
http://www.rachinsky.de/nicolas