I'm at 99% right now (30GB free) -- I'll free some space, test again every 5% and report back.
Interestingly, a dd if=/dev/zero of=fragtest bs=40k count=1;filefrag fragtest results in that file using 3 extents instead of 1 roughly every 10th-11th creation.
Just for reference, a fresh JFS on the same 7-disk RAID5/LVM partition gets 185MB/sec writes consistently.
Thanks for the help,
On Fri, 2007-01-19 at 01:38 -0500, Jason Fisher wrote:
> I have a 1.6TB jfs partition (Linux) that is roughly a year old. In
> this time, the write speed has managed to drop to 5MB/sec and it has
> become nearly unusable. I mainly use the RAID for mythtv, but
> recently it has become too slow for capturing.
> filefrag reports some 3GB files with 90,000 extents next to 3GB files
> with 18 extents. Many files with thousands of extents.
> I understand there are no defrag tools available for Linux, and I
> would rather not back the data up and restore as it's important, but
> just not important enough to warrant the time spent.
> Is there another way I can deal with these files?
> I copied a file with 3000 extents off the partition and onto a spare,
> deleted the original and copied the file back and ended up with 1100
> extents. An improvement, but would this method ever get performance
> back to a usable level?
I'm not sure if this will make much of a difference. Defragging the
existing files one at a time may not have much of an effect on the
remaining free space, so a new file being captured may be just as
fragmented as before.
> What if I were to fill the remaining space
> with dd after deleting the original/before copying it back?
I don't think this will do anything useful.
> Or should
> I concentrate on freeing up as much space as possible before copying
> any files to/from?
The more free space you have, the better. I don't know how close to
full your disk is, but you may want to try to maintain a certain amount
of free space and see how that affects performance. If you do find a
"sweet spot" such as having good performance when the disk is say 80%
full, I'd be interested to know that. Hopefully that percentage isn't
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