Re: ext3 sucks

[Arjan van de Ven <arjan infradead org>]

On Mon, 2005-10-24 at 13:49 -0400, Joshua Baker-LePain wrote:
> Well, on my servers with 3ware 7500-8 boards in hardware RAID5 mode it 
> does, and I thought the subject line might get a bit of attention. 
> Basically, no matter how I tune, I can't get anything even resembling 
> decent write speed out of hardware that used to run quite well.  I've 
> played with tuning both 'blockdev --setra' as well as 
> /sys/block/$DEVICE/queue/nr_requests, and nothing increases ext3 write 
> speed over 20MB/s on a single board.  To prove it isn't hardware, I also 
> tested using the centosplus kernel and XFS on the exact same array.  XFS 
> was able to get over 40MB/s on a single board.  When doing a RAID0 over 2 
> boards, ext3 maxed out at 35MB/s while XFS was able to do >100MB/s.  All 
> these tests were done using bonnie++ and a filesize >4x the amount of 
> system RAM.

did you set the journalling mode to write-back?
The default ext3 journalling mode is more strict than the XFS one, but
slower (so the trade off is data integrity vs speed); XFS is more
comparable with the writeback type. The performance difference is mostly
visible on new file creation...