On Thu, Feb 7, 2013 at 7:49 AM, Adam Goryachev <mailinglists@xxxxxxxxxxxxxxxxxxxxxx> wrote: >> >> I definitely see that. See below for a FIO run I just did on one of my RAID10s >> >> md2 : active raid10 sdb3[1] sdf3[5] sde3[4] sdc3[2] sdd3[3] sda3[0] >> 742343232 blocks super 1.2 32K chunks 2 near-copies [6/6] [UUUUUU] >> >> seq-read: (g=0): rw=read, bs=64K-64K/64K-64K/64K-64K, ioengine=libaio, >> iodepth=32 >> seq-write: (g=2): rw=write, bs=64K-64K/64K-64K/64K-64K, >> ioengine=libaio, iodepth=32 >> >> Run status group 0 (all jobs): >> READ: io=4096.0MB, aggrb=2149.3MB/s, minb=2149.3MB/s, >> maxb=2149.3MB/s, mint=1906msec, maxt=1906msec >> >> Run status group 2 (all jobs): >> WRITE: io=4096.0MB, aggrb=1168.7MB/s, minb=1168.7MB/s, >> maxb=1168.7MB/s, mint=3505msec, maxt=3505msec >> >> These drives are pretty fresh and my writes are a whole gig less than >> my read. Its not for lack of bandwidth either. > > Can you please show your command line used, so I can try a similar test > and see a comparison? > Seeing the 8MB second write in your other post you've definitely got something bound up somewhere. You're going to want to get as low as possible in your stack to verify the SSDs themselves are not the issue. If you have extra unpartitioned space try testing against that. You can just manually TRIM it afterwards to cleanup. If you can get decent IO against a single device you've got something wrong higher up. You'll have to find ways to test against each layer to find your issue. The tool I used is FIO: http://freecode.com/projects/fio The benchmark was pretty simple. Save the following to a file, adjust directory to where the test should write, and run it with ./fio [file]. You may need to adjust the size parameter smaller if your system will have trouble creating a 4g file. The filename option can also be a device if the directory option is removed. Just be very careful as the write test is destructive if done to a device instead of a filesystem. [global] bs=64k ioengine=libaio iodepth=32 size=4g direct=1 runtime=60 directory=/root filename=ssd.test.file [seq-read] rw=read stonewall [seq-write] rw=write stonewall -- Dave Cundiff System Administrator A2Hosting, Inc http://www.a2hosting.com -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
