On 05/05/11 07:08, Liam Kurmos wrote:
Thanks to all who replied on this. I somewhat naively assumed that having 2 disks with the same data would mean a similar read speed to raid0 should be the norm (and i think this is a very popular miss-conception). I was neglecting the seek time to skip alternate blocks which i guess must the flaw. In theory though if i was reading a larger file, couldn't one disk start reading at the beginning to a buffer and one start reading from half way ( assuming 2 disks) and hence get close to 2x single disk speed? as a separate question, what should be the theoretical performance of raid5? in my tests i read 1GB and throw away the data. dd if=/dev/md0 of=/dev/null bs=1M count=1000 With 4 fairly fast hdd's i get raid0: ~540MB/s raid10: 220MB/s raid5: ~165MB/s raid1: ~140MB/s (single disk speed) for 4 disks raid0 seems like suicide, but for my system drive the speed advantage is so great im tempted to try it anyway and try and use rsync to keep constant back up.
Try RAID10 with the far layout. It should give you streaming reads the same as RAID0 Brad -- 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
