Resizing PVs (was: Installation Impressions)

[Sam Sharpe]

On 5 February 2011 22:15, Nikolaus Rath <Nikolaus at rath.org> wrote:
> You can shrink a PV, but you will loose the extents that are stored in
> the space that you have truncated. I don't consider that resizing.

That's interesting. I do consider it resizing... It's not the function
of the pvresize command to move the LVs around so that it is possible
to downsize the PV. That's something that the admin must do.

If I use fdisk to resize a partition, is it fdisk's job to resize the
filesystem?

> From the same manpage that you looked up:
>
> ,----
> | pvresize will refuse to shrink PhysicalVolume if it has allocated
> | extents after where its new end would be. In the future, it should
> | relocate these elsewhere in the volume group if there is sufficient free
> | space, like pvmove does.
> `----

Yup, that is true - so you need to free up those extents first. Often
this is done by adding a second temporary PV to the VG.

> Unfortunately, pvmove can only move extends to other PVs but not to a
> different location in the same PV.

Yes, so it won't do exactly what you want in one command, so you have
to do it a different way. I have in the past added a second PV,
Extended the VG to this PV, then moved enough LVs to that second PV to
make reducing the original PV feasible. But the fact remains, that you
can shrink a Physical Volume.

> Why so aggressive?

I wasn't being particularly aggressive, but I do actually dislike
people saying (or abbreviating) "just for the record" when they are
incorrect or the facts are disputed. The only thing that goes in the
official record are the facts.

-- 
Sam