Re: I/O topology fixes for big physical block size

[Mike Snitzer <snitzer@redhat.com>]

On Thu, Sep 30 2010 at  1:07pm -0400,
Eric Sandeen <sandeen@redhat.com> wrote:

> On 09/30/2010 11:30 AM, Ted Ts'o wrote:
> > On Tue, Sep 28, 2010 at 04:36:42PM -0500, Eric Sandeen wrote:
> >> Ok, then it sounds like mkfs.ext4's refusal to make fs blocksize less
> >> than device physical sectorsize without -F is broken, and that should
> >> be removed.  I'd say issue a warning in the case but if there's a 16k
> >> physical device maybe there's no point in warning either?
> > 
> > If the device physical sectorsize is that big, should we perhaps use
> > that as a hint to align writes to that blocks aligned with that
> > physical sectorsize?  Right now we use the optimal I/O size, but if
> > the optimal I/O size is not specified and the physical sectorsize is,
> 
> I can't keep track of all the parameters, is it ever true that optimal
> I/O size isn't specified?

Yes optimal_io_size may be 0.  But minimum_io_size will always be scaled
up to at least match physical_block_size.

In any case: this 1MB physical_block_size device, which started this
thread, also has 1MB for both minimum_io_size and optimal_io_size.

Mike