[Launchpad-dev] [RFC] Taking source package branches to the next release

[Jonathan Lange]

On Fri, Aug 7, 2009 at 1:39 PM, Gavin
Panella<gavin.panella at canonical.com> wrote:
> From the BranchingUbuntu page:
>
>> Approximately 300GB of branch data.
>
> Is moving 300GB of data around in a single day going to cause any
> issues for backups? IS might be surprised :)
>

The idea would be to 'mv' the files, keeping them all on the same
partition. This won't require moving the actual data, just inodes.

>> 2. Swap the .bzr directories for the old branch and new branch using
>> filesystem operations.
>
> In the db, is there some indirection between branch names and their
> physical locations?

Yes. The location on disk is a function of the database Id.

> Could that be used to provide an atomic change
> instead? Swapping directories has a small window of brokeness and a
> chance of failure in the middle. If 16,000 of them are being done,
> even a small likelihood of failure could create many problems.
>

I'm not sure, I think that would require changing the Branch.id field
of the branches, which seems pretty off to me.

It's possible I'm missing something though -- I find it hard to think
about this kind of problem without pictures.

> Are all branches stored on the same filesystem? If not, the new branch
> should probably be created on the same filesystem as the old, or the
> .bzr swap could be costly.
>

Yeah they are. Good catch though.

jml