Dave Chinner wrote: > On Tue, Mar 09, 2010 at 01:16:01PM +0300, Michael Tokarev wrote: >> Karel Zak wrote: >>> I did almost all my tests with scsi_debug or MD RAID0 on scsi_debug. >>> It works as expected. >> Actually, for raid0, the alignment is questionable. Should it be a >> multiple of chunk size or whole stripe size? I'm not sure, both ways >> has bad and good sides.. But if it is the latter, the same issues >> pops up again: do a 3-disk raid0 and you'll have to align to 3*2^N. > > Yes, alignment is still needed, especially for filesystems that can > do stripe unit aligned allocation like XFS. If you don't align the > filesystem properly, all the data IO will be mis-aligned to the > underlying disks and stripe unit sized IO will hit multiple disks > rather than just one.... I understand alignment is needed, the question is if the alignment should be to chunk size or full-stripe size. In neither case it will be bad for underlying disks. /mjt -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
