2011/5/4 Liam Kurmos <quantum.leaf@xxxxxxxxx>: > 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. hum, you should consider you application..... for example, if you need a big ALTER TABLE (SQL database), that must be very fast to don´t stop your production server, you should use f2 or raid0 ehehehe but if you have a stable application that you need multiuser acess, raid1 or n2 layout could be better backup i´m running with raid10 f2, or raid1+raid0, and production machine i´m using raid1 and linear to get more space don´t forget to align partitions if you use it > > 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
