Re: One disk busy in RAID5?

2 messages, 2 authors, 2005-08-01 · open the first message on its own page

Re: One disk busy in RAID5?

From: Neil Brown <hidden>
Date: 2005-07-31 06:33:15

On Saturday July 30, scott-raid@riskboys.com wrote:
I'm doing a big rsync to my 5 disk RAID 5 partition and am seeing an
uneven loading of my disks.  The files are almost all huge video files.
Has anyone got any idea what I could have done wrong?

md6 : active raid5 sdi1[4] sdh1[3] sdg1[2] sdf1[1] sde1[0]
      976783360 blocks level 5, 128k chunk, algorithm 2 [5/5] [UUUUU]

The filesystem is ext3 created with 
mkfs.ext3 -R stride=32 /dev/md6
I suggest you ask on ext3-users@redhat.com.
I have seen references to this sort of thing before.  I think some
metadata gets aligned despite the '-R stride=' flag.
Also, I think the stride should be 128 (32 fs-blocks per chunk, 4
chunks per stripe).

NeilBrown

Re: One disk busy in RAID5?

From: Forrest Taylor <hidden>
Date: 2005-08-01 14:30:59

On Sun, 2005-07-31 at 00:33, Neil Brown wrote:
On Saturday July 30, scott-raid@riskboys.com wrote:
quoted
I'm doing a big rsync to my 5 disk RAID 5 partition and am seeing an
uneven loading of my disks.  The files are almost all huge video files.
Has anyone got any idea what I could have done wrong?

md6 : active raid5 sdi1[4] sdh1[3] sdg1[2] sdf1[1] sde1[0]
      976783360 blocks level 5, 128k chunk, algorithm 2 [5/5] [UUUUU]

The filesystem is ext3 created with 
mkfs.ext3 -R stride=32 /dev/md6
I suggest you ask on ext3-users@redhat.com.
I have seen references to this sort of thing before.  I think some
metadata gets aligned despite the '-R stride=' flag.
Also, I think the stride should be 128 (32 fs-blocks per chunk, 4
chunks per stripe).

NeilBrown
Speaking of which, how does one determine the stride size?  If I do:
  mdadm -C /dev/md0 -l 5 -c 64 -n 2 /dev/sd{ab}1
  mke2fs -j -b 4096 -R stride=???  /dev/md0

What should the stride size be--64x4?  Is the default chunk size still
64K?

Thanks,

Forrest
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