On Mon, Jun 02, 2008 at 10:09:46AM -0500, Jon Nelson wrote: > i can't show you raw write values, but I can show you raw read values > (after dropping the caches): > > >From dstat, this shows disks sdb, sdc, and sdd values in read (space) > write format, with the total on the end. > > Thus: > > 70M 0 : 71M 0 : 72M 0 : 213M 0 > 71M 0 : 70M 0 : 69M 0 : 210M 0 > 71M 0 : 73M 0 : 74M 0 : 217M 0 > > shows that I'm getting 70+- MB/s on each disk, combined to 210 to 217MB/s. > These are read values. > > I created a logical volume (50G), dropped the caches again, and issued: > > dd if=/dev/zero of=/dev/raid/test bs=64k > > and got from 100 to 150MB/s sustained write speeds. > NOTE: this is with a bitmap (internal) > Without a bitmap (removed for this test), I get a much more consistent > 130-150MB/s. 70 MB/s sounds like as expected. > dd reports a mere 70MB/s when complete. > When using oflag=direct, I get about 100MB/s combined, with a > "reported" speed of 51.9MB/s. > Since I'm using 3x drives, my total I/O is going to be about 2x what dd "sees". > > Does that help? It does not explain a 7 MB/s rate. the 52 MB/s writing seems as expected - maybe a bit slow, but not very slow. I do not know is a 3-disk raid10,f2 has specific performance problems. You could try the command (md3 being my raid) blockdev --setra 65536 /dev/md3 It solved some performance problems for me. Best regards keld -- 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
