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Re: XFS Performance on NetApp

To: Michael Monnerie <michael.monnerie@xxxxxxxxxxxxxxxxxxx>
Subject: Re: XFS Performance on NetApp
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 27 Oct 2010 10:10:07 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <201010270033.35894@xxxxxx>
References: <201010270033.35894@xxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
On Wed, Oct 27, 2010 at 12:33:35AM +0200, Michael Monnerie wrote:
> Does anybody have a report how XFS behaves on a NetApp storage with thin 
> provisioning? They have a completely "weird" storage, their WAFL (write 
> anywhere file layout) together with deduplication and other things make 
> me think the best is to not-at-all specify any "performance options" in 
> mkfs/mount, like sunit/swidth or largeio, swalloc, etc.
> 
> Does someone have information on that?

Not about the Netapp as such.

However, as a general rule thin provisioned storage will have
unpredictable performance characteristics as the block
number/physical location correlation is meaningless.

e.g. because the log is one of the first things written to a thinly
provisioned volume during mkfs, it is unlikely to be physically
located in the middle of the volume. Indeed, there's no guarantee
that it will even be on the same spindles as the rest of the
filesystem, and it may be sharing spindles with some other thin
volume....

So, you are right in assuming that it is best not to tune your
filesystem to a specific physical geometry because there generally
isn't one for thinly provisioned volumes. However, options that
reduce filesystem fragmentation (e.g. allocsize) still have value in
keeping the amount of metadata and ptotential seeks down...

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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