On Thu, 22 Mar 2007, Peter Rabbitson wrote:

Hi,
How does one determine the XFS sunit and swidth sizes for a software raid10
with 3 copies?

mkfs.xfs uses the GET_ARRAY_INFO ioctl to get the data it needs from 
software raid and select an appropriate sunit/swidth...

although i'm not sure i agree entirely with its choice for raid10:

                *sunit = md.chunk_size >> 9;
                *swidth = *sunit * md.raid_disks;

i'd think it would depend on the layout of the raid10 (near, far, 
offset)... for near2 on 4 disks i'd expect swidth to be only 2*sunit... 
but for far2 on 4 disks i'd expect 4*sunit... but i'm not sure.  it 
probably doesn't matter.

-dean