Re: [Jfs-discussion] Fragmentation and poor write speeds.
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From: Dave K. <sh...@li...> - 2007-01-19 13:34:11
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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 too low. > Thanks, > Jason -- David Kleikamp IBM Linux Technology Center |