[lvm-devel] [RFC PATCH v2] change default alignment of pe_start to 1MB

[Mike Snitzer]

On Mon, Aug 09 2010 at 12:28pm -0400,
Milan Broz <mbroz at redhat.com> wrote:

> On 08/06/2010 06:11 AM, Mike Snitzer wrote:
> > The following revised patch changes the LVM alignment detection
> > semantics to model what fdisk has elected to do:
> > - If the default value (1MB) is a multiple of the specified/detected
> >   alignment then just use the default.
> > - Otherwise, use the specified/detected value.
> > 
> > In practice this means we'll almost always use 1MB -- that is unless:
> > - the specified --dataalignment, MD's full stripe width, or the
> >   optimal_io_size exceeds 1MB
> > - the specified/detected value is not a power-of-2
> 
> patch not tested, but Ack for idea.
> (I just did independently the same for LUKS devices.)

Great.  And just one point of clarification: if --dataalignment is used
then the requested alignment is used (no additional logic is allowed to
change the requested value).

Mike