backups using LVM snapshots and "svnadmin lstxns"

[Ronan <ro...@furioustribe.com>]

I want to back up a filesystem on a Linux machine, by taking
an LVM snapshot of the filesystem then copying it to a remote
server.  However, there are Subversion repositories on the
filesystem, and I'm concerned that there could be a commit
under way to one or more of these repositories at the instant
that I take the snapshot, which could result in my getting a
corrupted SVN repository in the backup.

I think I have a solution to this problem, which I present in
the following PHP code.  (It should be intelligible to anyone
who knows a C-like language.)  Does anyone know whether the
solution will work?

  ######### code begins here

  do {
    make_snapshot();

    $transaction_found = FALSE;

    foreach ($repository_on_snapshot as $dir) {
      if(system("svnadmin lstxns $dir") !== '') {
        $transaction_found = TRUE;
        break;
      }
    }
  } while($transaction_found);

  # all the SVN repositories are consistent,
  # so continue with the backup...

  ######### code ends here

The SVN book strongly implies that the solution will work,
but I would prefer to have an explicit assurance on this point.

I'm not subscribed to this list, so please copy me on any
replies.

Re: backups using LVM snapshots and "svnadmin lstxns"

[Daniel Shahaf <d....@daniel.shahaf.name>]

Please read the in the archives the thread taking place YESTERDAY that
discusses LVM snapshots and validity.  If you still have any questions
after reading it --- do ask.

Cheers,

Daniel

Ronan wrote on Wed, Feb 15, 2012 at 11:35:25 +0000:
> I want to back up a filesystem on a Linux machine, by taking
> an LVM snapshot of the filesystem then copying it to a remote
> server.  However, there are Subversion repositories on the
> filesystem, and I'm concerned that there could be a commit
> under way to one or more of these repositories at the instant
> that I take the snapshot, which could result in my getting a
> corrupted SVN repository in the backup.
> 
> I think I have a solution to this problem, which I present in
> the following PHP code.  (It should be intelligible to anyone
> who knows a C-like language.)  Does anyone know whether the
> solution will work?
> 
>   ######### code begins here
> 
>   do {
>     make_snapshot();
> 
>     $transaction_found = FALSE;
> 
>     foreach ($repository_on_snapshot as $dir) {
>       if(system("svnadmin lstxns $dir") !== '') {
>         $transaction_found = TRUE;
>         break;
>       }
>     }
>   } while($transaction_found);
> 
>   # all the SVN repositories are consistent,
>   # so continue with the backup...
> 
>   ######### code ends here
> 
> The SVN book strongly implies that the solution will work,
> but I would prefer to have an explicit assurance on this point.
> 
> I'm not subscribed to this list, so please copy me on any
> replies.