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Re: Anyone using XFS in production on > 20TiB volumes?

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: Anyone using XFS in production on > 20TiB volumes?
From: Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>
Date: Thu, 23 Dec 2010 04:43:26 -0500 (EST)
Cc: Eric Sandeen <sandeen@xxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <20101223005630.GJ4907@dastard>
References: <alpine.DEB.2.00.1012221128440.5245@xxxxxxxxxxxxxxxx> <20101222175611.1c7d5190@xxxxxxxxxxxxxxxxxxxx> <4D124B71.9030401@xxxxxxxxxxx> <20101223012655.2681c596@xxxxxxxxxxxxxx> <alpine.DEB.2.00.1012221928050.7452@xxxxxxxxxxxxxxxx> <20101223005630.GJ4907@dastard>
User-agent: Alpine 2.00 (DEB 1167 2008-08-23)


On Thu, 23 Dec 2010, Dave Chinner wrote:

On Wed, Dec 22, 2010 at 07:28:29PM -0500, Justin Piszcz wrote:


On Thu, 23 Dec 2010, Emmanuel Florac wrote:

Le Wed, 22 Dec 2010 13:03:13 -0600 vous écriviez:

http://xfs.org/index.php/XFS_FAQ#Q:_I_want_to_tune_my_XFS_filesystems_for_.3Csomething.3E

which mentions getting your geometry right if it's hardware raid
that can't be detected automatically.

Just as a side note : I tried several times to manually set the
filesystem layout to precisely match the underlying hardware RAID
with sunit and swidth but didn't find that it made a noticeable
difference. On my 39.9 TB systems, the default agcount is 39, while the
optimum would be (theorically at least)  42.

Hi, I concur, for hardware raid (at least on 3ware cards) I have
found it makes no difference, thanks for confirming.

I'd constrain that statement to "no difference for the workloads
and hardware tested".

Indeed, testing an empty filesystem will often show no difference in
performance, because typically problems don't show up until you've
started to age the filesystem significantly. When the filesystem has
started to age, the difference between having done lots of stripe
unit/width aligned allocation vs none can be very significant....

Hence don't assume that because you can't see any difference on a
brand new, empty filesystem there never will be a difference over
the life of the filesytem...

Cheers,

Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx

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Hi Dave,

So for an 18 disk raid-6 with 256k stripe you would recommend:

mkfs.xfs with su=256k,sw=16 for optimal performance with inode64 mount option?

Justin.
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