Poor ext3 performance on RAID array

Andreas Dilger adilger at clusterfs.com
Wed Aug 8 23:21:21 UTC 2007

On Aug 08, 2007  15:21 -0500, Rene Salmon wrote:
> I am having some strange performance issues with ext3 and I am hoping to
> get some advice/hints on how to make this better.  First some background
> on the setup.
> We have a RAID 5 array 10+1+1 with one LUN.  That is 10 SATA drives one
> parity drive and one dedicated spare.  The LUN is about 6.5TB.
> Using a 2Gbit/sec fiber channel card I can do some dd writes to the raw
> device and get speeds close to 200Mbytes/sec which is more or less the
> max the card can do.
> Next I create an xfs file system on the LUN and do a dd to xfs and get
> speeds close to 150Mbytes/sec.
> I want to use ext3 not xfs so next I put ext3 on the lun.  Now when I do
> the dd to the ext3 lun I get 25-50Mbytes/sec depending on whether I have
> the Raid controller cache turned on or off. Getting 50MBytes/sec with
> the raid controller cache turned off.
> I know that ext3 should perform better so I must be doing something
> wrong.  Here is my mkfs.ext3
> mkfs.ext3 -b4096 -Tlagefile4 /dev/dm-0

You could also try out ext4, that's where the real performance improvements

Cheers, Andreas
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

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