Re: 4K drives, sectsz=512, bsize=4096

Nathan Scott
2010-08-31T22:33:57Z

----- "Michael Monnerie" <michael.monnerie@is.it-management.at> wrote:

> On Dienstag, 31. August 2010 Eric Sandeen wrote:
> > If you do it right (and especially vs. if you do it wrong) it
> > should be a bit faster if all IOs are 4k aligned on the disk.
>
> And that's what's interesting me: why? Won't XFS do all I/Os at
> minimum
> for a given block size? Or is it possible XFS does write only a single
> sector? I'd expect the smallest I/O size to be the block size, but it
> seems I'm wrong?

Log I/O and direct writes are sector sized & aligned.

> I guess there's no way to "convert" an existing XFS with
> sectsz=512,bsize=4096 to sectsz=4096,bsize=4096? Maybe that's only a
> flag that can be changed?

There's no way (other than dump, mkfs & restore), the filesystem is laid
out differently (most data structures, like superblocks and other metadata
become 4K aligned).

cheers.

--
Nathan