[mythtv-users] Horrendous RAID-6 performance

John Drescher drescherjm at gmail.com
Fri Mar 28 21:44:03 UTC 2008


On Fri, Mar 28, 2008 at 5:34 PM, Yan Seiner <yan at seiner.com> wrote:
> My system has a 1.2 TB RAID-6 formatted as a single ext3 partition.  All
>  was well for a while, then I had a minor crash, and had to repair the
>  raid. (manual fsck kind of repair).
>
>  Now I get absolutely horrible RAID performance:
>
>  selene:/var/log# hdparm -tT /dev/md10
>
>  /dev/md10:
>   Timing cached reads:   2472 MB in  2.00 seconds = 1236.69 MB/sec
>   Timing buffered disk reads:   10 MB in  3.23 seconds =   3.10 MB/sec
>
>  WTF?  Can anyone provide a clue on how to debug this?
>
>  I've been all through the system, nothing shows any sort of error, nothing
>  in the logs, mdadmin is happy, smartd is happy, the partition fsck's
>  clean.
>
>  Could this be because the system is getting full? (I'm clutching at straws
>  here.)
>
>  selene:/var/log# df /dev/md10
>  Filesystem           1K-blocks      Used Available Use% Mounted on
>  /dev/md10            1538311980 1279051236 243632396  84% /data
>
>  Is there some way to verify / rebuild the raid in-place?  I could get most
>  of the data off and reformat, but obviously I'd rather not....
>

can you post the output of cat /proc/mdstat

John


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