[mythtv-users] Horrendous RAID-6 performance

Yan Seiner yan at seiner.com
Fri Mar 28 21:34:54 UTC 2008


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....

--Yan

-- 
Windows is like a canary in a coal mine, it's the first thing to die on
your network.



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