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Re: Question regarding XFS on LVM over hardware RAID.

To: xfs <xfs@xxxxxxxxxxx>
Subject: Re: Question regarding XFS on LVM over hardware RAID.
From: "C. Morgan Hamill" <chamill@xxxxxxxxxxxx>
Date: Wed, 29 Jan 2014 14:11:59 -0500
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Thanks for the quick reply.

Excerpts from Eric Sandeen's message of 2014-01-29 10:07:15 -0500:
> The stripe unit and width are units of geometry of the underlying
> storage; a filesystem will span some number of stripe units, depending
> on its size.
> 
> So no, the filesystem's notion of stripe geometry does not change
> with the filesystem size.
> 
> You do want to make sure that stripe geometry is correct and aligned
> from top to bottom.

Just to make sure I've understood, for 3 14-disk RAID 6 groups striped
together into a single RAID 60, with stripe units of 128k, split up into
some number of LVM logical volumes, I'd create the filesystems with the
following:

    mkfs.xfs -d su=128k,sw=36 ...

for all of the filesystems, regardless of how many and what size they
were.  Does that sound right?

> I helped write up the RHEL storage admin guide, and there are some
> nice words about geometry and alignment in there:
> 
> https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/ch-iolimits.html

Thanks for the resource!
--
Morgan Hamill

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