From: Stan Hoeppner <stan@hardwarefreak.com>
To: Stewart Webb <stew@messeduphare.co.uk>
Cc: xfs@oss.sgi.com
Subject: Re: xfs hardware RAID alignment over linear lvm
Date: Wed, 25 Sep 2013 16:18:31 -0500 [thread overview]
Message-ID: <52435327.9080607@hardwarefreak.com> (raw)
In-Reply-To: <CAE3v2EaODFud_S_BzuSjtwGwuNBXhvL0RiPB1P5QroF45Obwbw@mail.gmail.com>
On 9/25/2013 7:56 AM, Stewart Webb wrote:
> Hi All,
Hi Stewart,
> I am trying to do the following:
> 3 x Hardware RAID Cards each with a raid 6 volume of 12 disks presented to
> the OS
> all raid units have a "stripe size" of 512 KB
Just for future reference so you're using correct terminology, a value
of 512KB is surely your XFS su value, also called a "strip" in LSI
terminology, or a "chunk" in Linux software md/RAID terminology. This
is the amount of data written to each data spindle (excluding parity) in
the array.
"Stripe size" is a synonym of XFS sw, which is su * #disks. This is the
amount of data written across the full RAID stripe (excluding parity).
> so given the info on the xfs.org wiki - I sould give each filesystem a
> sunit of 512 KB and a swidth of 10 (because RAID 6 has 2 parity disks)
Partially correct. If you format each /dev/[device] presented by the
RAID controller with an XFS filesystem, 3 filesystems total, then your
values above are correct. EXCEPT you must use the su/sw parameters in
mkfs.xfs if using BYTE values. See mkfs.xfs(8)
> all well and good
>
> But - I would like to use Linear LVM to bring all 3 cards into 1 logical
> volume -
> here is where my question crops up:
> Does this effect how I need to align the filesystem?
In the case of a concatenation, which is what LVM linear is, you should
use an XFS alignment identical to that for a single array as above.
--
Stan
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next prev parent reply other threads:[~2013-09-25 21:18 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-25 12:56 xfs hardware RAID alignment over linear lvm Stewart Webb
2013-09-25 21:18 ` Stan Hoeppner [this message]
2013-09-25 21:34 ` Chris Murphy
2013-09-25 21:48 ` Stan Hoeppner
2013-09-25 21:53 ` Chris Murphy
2013-09-25 21:57 ` Dave Chinner
2013-09-26 8:44 ` Stan Hoeppner
2013-09-26 8:55 ` Stewart Webb
2013-09-26 9:22 ` Stan Hoeppner
2013-09-26 9:28 ` Stewart Webb
2013-09-26 21:58 ` Dave Chinner
2013-09-27 1:10 ` Stan Hoeppner
2013-09-27 12:23 ` Stewart Webb
2013-09-27 13:09 ` Stan Hoeppner
2013-09-27 13:29 ` Stewart Webb
2013-09-28 14:54 ` Stan Hoeppner
2013-09-30 8:48 ` Stewart Webb
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