On Mon, Aug 30, 2010 at 09:56:16AM +0200, Michael Monnerie wrote: > I have 2x 2TB 4K sector drives, joined with LVM to RAID-0. On top of > that, I created an XFS, but that has sectsz=512. > > Will there be any real difference if I re-format with sectsz=4096? > AFAIK, XFS will do I/O based on block size, so the sector size doesn't > do any harm. Is that correct? As nathan mentioned XFS issues log I/O based on the sector size, and we do allow direct I/O down to the sector size. That's two reasons why or why you don't want a 4096 byte sector size. Depending on the rmv implementation of the drive log I/O might be really slow if you set the 512 byte sector size. On the other hand there's lots of applications that have the 512 byte alignment for direct I/O hardcoded, which will break if you have a larger sector size. That's one of the fun things 4k sector size disks will bring up, especially the real 4k SAS disks that do not accept any I/O smaller than that. > A question for LVM: Is there anything I need to tell to LVM to let it > know that those are 4K sector drives and I/O should be aligned to that? > Drives are reported as 512b sectors, but really are 4K. There seems to > be no way to instruct the kernel to see those drives as 4K drives. If you have a recent enough LVM all metdata is aligned on 1MB boundaries which will do just fine. _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
