On 20.03.2003 06:04 Mark Mayo wrote:
On Wed, Mar 19, 2003 at 02:39:26PM -0600, Steve Lord wrote:
>
> Also, pay attention to the mkfs output, the sunit and swidth lines,
> these control how data will get layed out. You want to make sure they
> line up with your device configuration. This may or may not happen
> automatically depending on your setup. Read the mkfs.xfs man page for
> how to control them yourself.
Ah. I'm just trying XFS for the first time and also have some tuning
questions!
Is the general recommendation to set sunit/su and swidth/sw when running
on a hardware RAID system? In my case, I have a bunch of volumes created
on an IBM FAStT700 SAN (rebranded LSI 4884, like the SGI SAN Server
1000). The RAID controller lets me adjust "segment size" from 8-256K,
with a default of 64KB on a RAID5 volume. The docs say "A segment is the
amount of data, in kilobytes, that the controller writes on a single
drive in a logical drive before writing data on the next drive." Am I
correct when I interpret this as the "strip unit size" defined in the
mkfs.xfs man page?
Assuming I'm on the right track then, since I have 512 byte data
blocks, the 64KB stripe takes up 128 blocks. I have 12 drives in the
stripe, so to create a XFS FS I'd run:
mkfs.xfs -d sunit=128,swidth=1536
or
mkfs.xfs -d su=64k,sw=768k
On Raid5 setups switdh should be (n-1)*sunit, I think. In your case that would
be 11*128, not 12*128.
Christian
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