On Fri, 2010-04-02 at 17:45 +0800, Lu Wang wrote: > Hi, > We set up a test file system with same patrition and same hardware. > When the system is empty, the disk I/O is less fragemented.
So, I think you now have confirmation as to what's causing your disk I/O fragmentation problem on your production system, yes? > However, the disk I/O in flight is still low (mostly at "1"). Is there any > way to increase this value through configuration? I think you are chasing a red herring. The number of disk I/Os in flight is only an indicator as to what could be wrong when other things are not working correctly. But as you can see from your brw_stats, the only items that are not absolutely *perfect* are that 2% of your disk I/Os were fragmented: > read | write > disk fragmented I/Os ios % cum % | ios % cum % > 1: 0 0 0 | 2289 97 97 > 2: 0 0 0 | 69 2 100 and 4% of your disk I/Os were not a full 1M. > read | write > disk I/O size ios % cum % | ios % cum % > 8K: 0 0 0 | 1 0 0 > 16K: 0 0 0 | 1 0 0 > 32K: 0 0 0 | 0 0 0 > 64K: 0 0 0 | 1 0 0 > 128K: 0 0 0 | 4 0 0 > 256K: 0 0 0 | 12 0 0 > 512K: 0 0 0 | 58 2 3 > 1M: 0 0 0 | 2350 96 100 I would think those two small deviations from perfect would be within the realm of acceptable, yes? If you agree then you need to stop chasing the disk I/Os in flight. One likely explanation is simply that the disk(s) is(are) able to drain the I/Os in flight as fast as the OST(s) is(are) able to push them -- which is good! Cheers, b.
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