Hello, I've been running some tests on a bunch of disks lately and came across a strange result that I'm struggling to explain. I built a 20-device raid10 md array with SSDs and ran several fio tests on it. The randwrite test really stands out because the IOPS starts out fairly low, around 800 IOPS, but within a few seconds climbs up to about 70K IOPS, which is nearly three times higher than the IOPS I'm getting with the randread test (25K). I tried disabling the drive caches using hdparm -W 0, and also disabling the internal write-intent bitmap on the md array, but the results are the same. Here are the test parameters: ioengine=libaio invalidate=1 ramp_time=10 iodepth=4 runtime=60 time_based direct=1 randrepeat=0 filename=/dev/md1 bs=4k rw=randwrite I generated some gnuplot graphs from the logs: randread test: https://imgur.com/dj25FFH randwrite test: https://imgur.com/BuZVNmh Thanks, -- Jerome -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
