Cheers Roberto, I've got the gist of the far layout from looking at wikipedia. There is some clever stuff going on that i had never considered. i'm going for f2 for my system drive. Liam On Thu, May 5, 2011 at 1:25 AM, Roberto Spadim <roberto@xxxxxxxxxxxxx> wrote: > raid10,f2 is a stripe configuration and mirror too, think about it like this: > > disk 1,2,3,4 > /dev/md0 = raid1 (1,2) > /dev/md1 = raid1 (3,4) > > /dev/md2 = raid0 (stripe) (md0,md1) <--- it´s near raid10 > > > > > 2011/5/4 Liam Kurmos <quantum.leaf@xxxxxxxxx>: >> incidentally what does the f2 layout do that it performs so much >> better than the default? >> >> Liam >> >> >> On Thu, May 5, 2011 at 1:14 AM, Liam Kurmos <quantum.leaf@xxxxxxxxx> wrote: >>> Thanks guys! >>> >>> >>> >>>>> raid10: 220MB/s >>>> >>>> Assuming the default 'n2' layout, I would expect 2*140 or 280, so this is a >>>> little slow. Try "--layout=f2" and see what you get (should be more like >>>> RAID0). >>> >>> >>> mdadm -C /dev/md0 --level=raid10 --layout=f2 --raid-devices=4 >>> /dev/sda1 /dev/sdc1 /dev/sdd1 /dev/sde1 >>> >>> dd if=/dev/md0 of=/dev/null bs=1M count=1000 >>> 1000+0 records in >>> 1000+0 records out >>> 1048576000 bytes (1.0 GB) copied, 2.23352 s, 469 MB/s >>> >>> :D >>> >>> awesome!! >>> >>>> >>>>> raid5: ~165MB/s >>>> >>>> I would expect 3*140 or 420, so this is very slow. I wonder if read-ahead is >>>> set badly. >>> >>>> Can you: >>>> blockdev --getra /dev/md0 >>>> multiply the number it gives you by 8 and give it back with >>>> blockdev --setra NUMBER /dev/md0 >>>> >>> >>> genius. >>> >>> im not really sure what this did but it totally fixed the problem. >>> >>> look ahead was 768, set it 6144 and immediately got 400MB/s >>>> >>>>> raid1: ~140MB/s (single disk speed) >>>> >>>> as expected. >>>> >>>>> >>>>> 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. >>>> >>>> If you have somewhere to rsync to, then you have more disks so RAID10 might >>>> be an answer... but I suspect you cannot move disks around that freely :-) >>>> >>> >>> no need now! f2 layout is awesome. >>> >>> many thanks, >>> >>> Liam >>> >>> >>> >>>> NeilBrown >>>> >>>> >>>> >>>>> >>>>> cheers for you responses, >>>>> >>>>> Liam >>>> >>> >> -- >> 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 >> > > > > -- > Roberto Spadim > Spadim Technology / SPAEmpresarial > -- 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
