On Thu, Jan 06, 2011 at 05:02:47PM +0000, Mister IT Guru wrote:
> I've been trying to get my head around virtual full backups.
> 
> Now, from my understanding, (i'm 80% through my work day, shut down 20 
> tickets, and had to deal with too many user incidents for my liking, so 
> please bare with me if I say something stupid!), virtual fulls can be 
> run on the same pool as a real 'recent' full has been run on, and it 
> will create a new full based on all the latest files still in the pool. 
> It then takes these files, and only take the latest changed files, from 
> the client to create a new usable full backup, which should pretty much 
> take the same time as between and incremental and a differential.
> 
> If this is the case, then I can slash my backup times, from 5 hours per 
> host, to around 20 minutes, which is something I think would be pretty 
> frikkin' awesome! Feel free to comment, and suggest :)

No, it doesn't take the latest files from the client.

It would solve a couple of problems that I have if that is what it did though.

A VirtualFull combines previous backups into a single backup that is
equivalent to a Full.

So, if you have a schedule like this:

Monday:    Incremental
Tuesday:   Incremental
Wednesday: Incremental
Thursday:  Incremental
Friday:    Incremental
Saturday:  Incremental
Sunday:    Incremental

You can't, say, just do this:

Monday:    Incremental
Tuesday:   Incremental
Wednesday: Incremental
Thursday:  VirtualFull
Friday:    Incremental
Saturday:  Incremental
Sunday:    Incremental

You actually have to do this, otherwise you don't get a backup for that day:

Monday:    Incremental
Tuesday:   Incremental
Wednesday: Incremental
Thursday:  VirtualFull plus seperate Incremental
Friday:    Incremental
Saturday:  Incremental
Sunday:    Incremental

And that means that you get into problems with the VirtualFull and Incremental
overlapping and getting in each other's way.

With my configuration, a VirtualFull sometimes prevents an Incremental from
running, because the VirtualFull took too long (or vice versa). I have not been
able to solve this, because every idea that I've come up with either doesn't
work or makes something else happen that is worse.

So, I would be very pleased if a VirtualFull also grabbed new files from the
client.


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