[ ... poor dead horse of alignment :-) ... ] mike> Right now I have my trusty 4 DISK RAID-5 with a CHUNKSIZE mike> of 256KB, thus having a stripe-size of 1MB. A largish chunk size with a largish stripe size may not be a particularly good idea for sequential IO, more for multithreaded access or for random access perhaps. mike> Version 1.03c ------Sequential Output------ [ ... ] mike> -Per Chr- --Block-- -Rewrite- [ ... ] mike> Machine Size K/sec %CP K/sec %CP K/sec %CP [ ... ] mike> xfs 8G 49398 43 26252 21 [ ... ] mike> lvm-chunkaligned 8G 45937 42 23711 24 [ ... ] mike> lvm-stripealigne 8G 49271 43 24401 25 [ ... ] mike> As you can see it apparently does make a difference if you mike> stripe align or not, [ ... ] But it should make a *much* bigger difference, and a 3+1 RAID5 should perform *a lot* better. As in 100-150MB/s (factor of 2-3 over a single disk) reading and (if aligned) writing. Perhaps there is some problem with your IO subsystem (USB drives? 4 ATA drives attached to only 2 channels? 5-10 year old disks?). BTW, Bonnie 1.03 or Bonnie++ or Iozone are not necessarily the best way to check things, I recommend Bonnie 1.14 with the options '-u -y -o_direct'. -- 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
