Hi,

Les Mikesell wrote on 2017-04-21 18:39:59 -0500 [Re: [BackupPC-users] BackupPC 
4.1.1 and NFS shares]:
> On Fri, Apr 21, 2017 at 5:09 PM, Bedynek, Matthew J. <bedynekmj AT ornl DOT 
> gov> wrote:
> > With version 3 I am using Rsync instead of tar to backup a NFS share which
> > the backupPC host has direct access to. [...] with version 4, there have
> > been changes to rsync such that am forced to use tar for a local copy.

if that is really the case, I would consider it a bug. However, I would
suspect that you could set

        $Conf {RsyncSshArgs} = [ '-e', '/usr/bin/sudo -u username -p' ];

(this is an untested hack ... I'm guessing rsync will append a hostname which
the sudo '-p' option will silently swallow) to get the equivalent of your
V3 settings:

> > [...]
> > $Conf{RsyncClientCmd} = 'sudo -u username $rsyncPath $argList+';
> > $Conf{RsyncClientRestoreCmd} = 'sudo -u username $rsyncPath $argList+???;

If that doesn't work, you could use a script instead and modify the
arguments in any way you need to.

> > I believe the RsyncClientCmd and RsyncClientRestoreCmd are gone in V4.

Correct.

> > I did get Rsync to work with V4 but it seems to ssh to localhost which
> > consumes additional host resources.

Yes, and there might be other valid reasons not to want that (e.g. not running
sshd on the host).

> > Rsync isn???t a big deal [...]

Well, I would think it is ... as you say yourself ...

> > [...] but am I correct in reading that Rsync might be better for
> > incremental backups in terms of handling deletions?

Yes. It handles them. tar doesn't. Period. And, more important, it handles
files not present in your reference backup (or modified since then) that can't
be caught by comparing timestamps (renamed, moved into the backup set,
extracted from an archive, included by changing in-/excludes, 'touch'ed to a
past date, ...). I wouldn't want to go back to tar any more than use SMB ...

> If you think about what rysnc is supposed to do, it doesn't make much
> sense to run both ends locally accessing data over NFS.

I tend to disagree. As far as I have understood Matthew's situation, rsync
is *supposed to* give more exact backups than tar, which it will do just
fine running both ends locally accessing data over NFS. And, I believe,
we're talking about his application of rsync here, not yours.

> For any file that is not skipped by the timestamp/length check in
> incrementals, you are going to read the entire file over NFS so rsync
> can compute the differences (where the usual point is to only send the
> differences over the network).

This is worth pointing out, but, again, there may be reasons to do this.
tar certainly won't do any better - it will also read the complete content
of any file not skipped over NFS. And the 'usual point' of running rsync
locally instead of tar is getting more exact incremental backups, not saving
bandwidth.

> Is there any way you can run rsync remotely against the NFS host instead?

This would save bandwidth, and it would spread some of the load over two
machines, which is either good or bad, depending on whether you want the
extra CPU load on your NFS server or not. During your backup window, this
is likely not an issue, but your mileage may vary. In any case, if you could
spare the bandwidth with BackupPC V3, there is no reason to get overly worried
now. You can try to tune your backup system to better performance or leave it
as it is.

Don't get me wrong - I'm not advising *against* changing to rsync over ssh to
the NFS server. I've been there myself. I've gone from (tar over NFS) ->
(rsync over NFS) -> (rsync over ssh). I'm just saying it doesn't seem to be
*essential*, as you didn't state any problems you had with BackupPC V3.

Regards,
Holger

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