"Martin K. Petersen" wrote:
>
> >>>>> "Anuradha" == Anuradha Ratnaweera <anuradha@xxxxxxx> writes:
>
> Anuradha> Is there any advantage in specifying chunk size etc. when
> Anuradha> running mkfs.xfs?
>
> For RAID1, no. For RAID0 and RAID5, potentially.
>
> Anuradha> If yes, where is it documented? I went through what is on
> Anuradha> the mkfs.xfs man page but is not inadaquate.
>
> Have you read the sections about sunit and swidth?
Yup. Still doesn't make much sense to me. It sounds like swidth is
analogous to chunk-size in software raid, but what is sunit?
And are 'sw' and 'su' just the abreviated forms of swidth and sunit,
respectively?
>
> In general mkfs.xfs will do the right thing. As the man page states,
> when you run mkfs on an LVM or MD device it will automagically extract
> the stripe unit and stripe width.
>
> If you have a hardware RAID device, however, you'll have to specify
> these parameters manually to match the configuration of your device.
So, to wit, in our systems we have 2, 8 disk HW RAID5 arrays which are SW
RAID0 (striped) together. The HW chunk size is 64k (this is hardcoded).
The SW chunk size is 512k. I wish that I could make this 448k (so one SW
chunk goes to one array, with the left over used as the parity chunk), but
that's not possible.
So, xfs_info shows this:
[root@sdssdp10 dp]# xfs_info /export/data/dp10.a/
meta-data=/export/data/dp10.a isize=512 agcount=268, agsize=1048576
blks
data = bsize=4096 blocks=280145408, imaxpct=25
= sunit=128 swidth=256 blks, unwritten=0
naming =version 2 bsize=4096
log =internal bsize=4096 blocks=32768
realtime =none extsz=1048576 blocks=0, rtextents=0
Why? Shouldn't swidth be 1000? And about sunit... well, I'm just confused
about what that should be.
>
> --
> Martin K. Petersen, Principal Linux Consultant, Linuxcare, Inc.
^^^^^^^^^
'bout damn time. :-)
Cheers,
Dan
--
Dan Yocum
Sloan Digital Sky Survey, Fermilab 630.840.6509
yocum@xxxxxxxx, http://www.sdss.org
SDSS. Mapping the Universe.
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