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Re: ext3/kjournald overhead



On Tue, Nov 06, 2001 at 03:01:42PM -0800, Carlos Knowlton wrote:
> Hi,
> 
> I've recently installed ext3 on an 800MB RAID5
> (software) array.  I am running RedHat Linux 7.1 with
> the Linux kernel 2.4.12-ac3 on a 1GHz Pentium system
> with 128MB RAM.  I am seeing a significant amount of
> write operation slowdown when running ext3 (and
> kjournald), as opposed to my old ext2.  The problem
> seems to be associated with the times that kjournald
> is accessing the disk.  At those moments, my CPU
> utilization peaks, and network transfer is nearly
> halted until kjournald is finished. 
> 
> I read in an archive of a Linux Symposium on 20 July,
> 2000 by Dr. Stephen Tweedie that, at that time, actual
> file data was being journaled as opposed to just
> metadata.  It looked like the plan was to fix that. 
> Has this been done?  If so, what else can I do to
> relieve this bottleneck?
> 
> I'm using this machine as a DV file repository, and am
> capturing video to it in real-time, so any delay
> spoils the capture session.  Any clues?
> 
> TIA,
> 

You can try a larger journal file.  You'll have to remove the current
journal flag, fsck, and recreate a larger journal...

There are three modes you can choose, ordered (default), data (full data
journal), or writeback (possibly fastest, but no guarantees that ext2 didn't
also).

Mike





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