XFS Performance on NetApp

XFS Performance on NetApp

[Michael Monnerie]

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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?

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Re: XFS Performance on NetApp

[Dave Chinner]

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@fromorbit.com

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Re: XFS Performance on NetApp

[Michael Monnerie]

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On Mittwoch, 27. Oktober 2010 Dave Chinner wrote:
> However, options that
> reduce filesystem fragmentation (e.g. allocsize) still have value in
> keeping the amount of metadata and ptotential seeks down...

Yes, but for NetApp: maybe. With this whole deduplication thingy, I 
wonder if even such a simple assumption is true. And then some people 
make a snapshot every hour, whichmeans your log will wander around on 
the storage anyway. So it's best to "just use it".

Another thing just crosses my mind: on a thin provisioned system, would 
the TRIM command be useful? Do such storages recognise this command? It 
would be very clever, I think. Let's say you run xfs_fsr, that would 
allow the upper layer to relaim unused space. Would that be the storage 
or XenServer/VMware which needs to understand this command?

-- 
mit freundlichen Grüssen,
Michael Monnerie, Ing. BSc

it-management Internet Services
http://proteger.at [gesprochen: Prot-e-schee]
Tel: 0660 / 415 65 31

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