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List:       linux-xfs
Subject:    Re: Anyone using XFS in production on > 20TiB volumes?
From:       Justin Piszcz <jpiszcz () lucidpixels ! com>
Date:       2010-12-23 9:43:26
Message-ID: alpine.DEB.2.00.1012230442150.7452 () p34 ! internal ! lan
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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@fromorbit.com
>
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> xfs@oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs
>

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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