Holger Parplies wrote at about 03:46:42 +0100 on Friday, March 15, 2013:
 > Hi,
 > 
 > Les Mikesell wrote on 2013-03-14 13:18:53 -0500 [Re: [BackupPC-users] Per-PC 
 > pools]:
 > > I'm still somewhat curious about why you dismissed virtual machines,
 > > which seem to me like a more obvious way to divvy up some
 > > partly-shared resources - and would offer a cleaner separation of
 > > control and better (still not great) methods to migrate to
 > > new/different hardware later.
 > 
 > and, in particular, would require no code changes at all. Yes, I'm curious,
 > too.
 > 
 > Concerning the code, I won't do more than have a quick glance at it, because
 > I'm not convinced it's a good idea. What the quick glance tells me, is that
 > the patch is next to unreadable, because it's not in unified format (i.e. no
 > context).
 > So, you seem to change PoolDir and CPoolDir in the library (though I don't 
 > see
 > where; let's hope your code is always executed before some part of BackupPC
 > tries to access the pool). That basically avoids touching any code in 
 > PoolWrite
 > and probably BackupPC_link. And by having a string setting for the pool
 > location, you enable pool sharing in a simple way. But you (i.e. the
 > administrator of the BackupPC instance) had better get the configuration 
 > right
 > (i.e. have the relevant pc/ and *pool/ directories on a common file system).
 > You don't seem to have checks for hard-linking capability. There's not much
 > help from the software in case of configuration errors.
 > 
 > You had better hope that the code consequently uses the PoolDir and CPoolDir
 > settings and not $TopDir/{c,}pool (easy enough to check). You probably 
 > remember
 > that it was a long standing bug that you couldn't set $Conf{TopDir} with the
 > desired effect ...
 > 
 > Furthermore, you lose the ability to use one BackupPC::Lib object for more
 > than one host (presuming you need the pool location). BackupPC probably
 > doesn't do that (I'm guessing), but I don't think this is a documented or
 > intended property.
 > 
 > While you might successfully use the code virtually forever, I would strongly
 > discourage anyone else from using it. There is just too much you need to
 > understand and have in mind. It's sort of half-automatic, because only half 
 > of
 > the consistency checks are done by the software. And by exposing the *PoolDir
 > settings to the web gui, you are suggesting that they are (changeable)
 > configuration options, while in reality they are descriptions of your disk
 > layout to BackupPC. I'd probably have preferred a fixed setting of
 > "../{c,}pool" relative to the host pc/ directory - i.e. use the pool on the 
 > FS
 > where the pc/ directory is. That is less flexible, but also less error-prone.
 > 

Beats me how this would work without also changing all the things
referencing the location of the pc tree (remember the super sensitive
OP specifically talked about using separate filesystems). In
particular, I see no reference to changes made to
BackupPC_link. Because as we all know, the pc tree and pool have to be
on the same filesystems... Then again no changes have been made to the
routine that checks for linkability so maybe the OP will never know
about such coding lapses.

Also, based on my playing with the code in Lib.pm and various other
modules, I seem to recall many more hard-coded references to pool
vs. cpool. Of course, it's possible that the OP got lucky and things
just somehow still work, but I sure as heck wouldn't count on it...

The fact that the OP doesn't know how to use standard patch format
doesn't give me a lot of confidence...

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