Re: swidth with mdadm and RAID6

[Shailendra Tripathi <stripathi@xxxxxxxxx>]

Can you list the output of
1. cat /proc/mdstat
2. the command to create 8+2 RAID6 with one spare ?
3. and output of following:
   xfs_db -r /dev/md*
   xfs_db> sb
   xfs_db> p

-shailendra

Steve Cousins wrote:
> I have a RAID6 array of 11 500 GB drives using mdadm.  There is one
> hot-spare so the number of data drives is 8.  I used mkfs.xfs with
> defaults to create the file system and it seemed to pick up the chunk size
> I used correctly (64K) but I think it got the swidth wrong.  Here is what
> xfs_info says:
>
> ===========================================================================
> meta-data=/dev/md0               isize=256    agcount=32, agsize=30524160
> blks
>          =                       sectsz=4096  attr=0
> data     =                       bsize=4096   blocks=976772992, imaxpct=25
>          =                       sunit=16     swidth=144 blks, unwritten=1
> naming   =version 2              bsize=4096
> log      =internal               bsize=4096   blocks=32768, version=2
>          =                       sectsz=4096  sunit=1 blks
> realtime =none                   extsz=589824 blocks=0, rtextents=0
> ===========================================================================
>
> So, sunit*bsize=64K, but swidth=144 and swidth/sunit=9 so it looks like it
> thought there were 9 data drives instead of 8.  
>
> Am I diagnosing this correctly?  Should I recreate the array and
> explicitly set sunit=16 and swidth=128?
>
> Thanks for your help.
>
> Steve
> ______________________________________________________________________
>  Steve Cousins, Ocean Modeling Group    Email: cousins@xxxxxxxxxxxxxx
>  Marine Sciences, 452 Aubert Hall       http://rocky.umeoce.maine.edu
>  Univ. of Maine, Orono, ME 04469        Phone: (207) 581-4302