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
