[OpenAFS] Incremental backups

[Tom Fitzgerald]

> >> 1) Aside from needlessly increasing the size of the dump, there's
> >>    no harm in setting the -time of an incremental dump to be
> >>    substantially earlier than it needs to be.
> > In my experience, you are correct.
> 
> I wouldn't go _substancially_ earlier, but I concur that you're correct. I 
> assume that you're worried about the conversion of wall time in your 
> timezone to epoch time wrt DST changes?

No, I'm assuming everything is UTC-based.  This is general paranoia
around the system clock being shifted back due to a time-
synchronization event or some such.

>  I'd personally recommend a "vos backup" immediately before your 
> "vos dump". That way a "vos exam" of the backup volume will always reveal 
> the last time the volume was actually dumped to your media.

Unfortunately this leads to .backup volume creation times being
spread over several hours.  This makes it hard to tell users when
they can expect their .backup volumes to be updated.  I like doing
all the vos backups in a burst, and then vos dumps taking as long
as they need.  I've never needed to know the exact time a volume
was written to media, as opposed to the exact time that it's a
snapshot of.