On Mar 12, 2008, at 20:54, Peter Grandi wrote:
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 [ ... ] 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.
I think for my setup here the numbers are okay.All four disk are a attached to a 4port SATA PCI card. Yes no typo, there is no "e" at the end. :)
Thus ~100MB looks like the optimum I will get out of this setup for reading, regardless of the number of disks. If I had the money, I would definitly go with something faster, attached to PCIe and a RAID-10.
But for now this rig has to do the job.All I am trying to do right now is keeping the difference between MD +XFS and MD+LVM+XFS as small as possible.
Kind regards, Michael
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