LVM Snapshot merging? [SOLVED]

[Richard Shaw]

On Fri, May 14, 2010 at 3:32 PM, Joseph L. Casale
<jcasale at activenetwerx.com> wrote:
>>To answer my own question here. The required bits (kernel, lvm,
>>device-mapper) appear to be available between F13 and F13-testing.
>>Since I'll be reinstalling for F13 I decided to go ahead and install
>>the F13 packages in F12 to see what happened. Everything appears to be
>>working fine.
>
> Richard,
> That's slick, so what's your procedure, do you just snap the root and
> maintain that until you're satisfied or do you boot from a snapshot?

>From my research I've found that you can treat the snapshot just like
another block device so it is possible to boot to it, however, in the
particular case of upgrading Fedora (or another major piece of
software) the typical use case is to create the snapshot as a safety
measure and upgrade the origin volume. If all goes well you drop the
snapshot and go on. If something goes wrong you merge the snapshot
back onto the origin and it's like it never happened.

The hardest decision to make regarding snapshot volumes is how big to
make them. You need to make sure it is big enough to store all the
changed bits and a log file. So in the case of upgrading Fedora I
would create one as big as a standard install (including any packages
you typically add after an install) plus a little bit. You don't want
to fill the snapshot volume or it is dropped automatically.

Richard