[TAG] Backup software/strategies

[Ben Okopnik]

On Sat, Jul 14, 2007 at 01:18:58PM +0200, Ren?? Pfeiffer wrote:
> On Jul 13, 2007 at 1420 -0400, Ben Okopnik appeared and said:
> > On Thu, Jul 12, 2007 at 09:17:28AM +0530, Kapil Hari Paranjape wrote:
> > [...]
> > > To that one can add the fact the laptops are not
> > > "always on" so that "cron" type scheduling is irrelevant. 
> > 
> > This, of course, is why I mentioned "at" - which will either run at the
> > specified time, or keep retrying if it misses the original schedule.
> 
> Shouldn't anacron take care of this? AFAIK anacron checks for missed
> cron job since the last boot and reschedules them. Provided that the
> cron jobs check for the presence of a suitable backup device/server (and
> don't offer all data to the frist device in range with the right IP
> address) this could work, don't you think?

Ah. I was thinking of "anacron" when I said "at". Right.
 
> > > So one approach is to periodically schedule "laptop maintenance
> > > mornings":
> > 
> > Which brings us back to the original problem. "Every other Tuesday
> > where the date is not divisible by 3 or 7 and is not within 4 days of
> > the end of month" can be scheduled; "7 days after last backup assuming
> > that I'm at home, otherwise as soon as I get home and have had a
> > chance to unpack and catch up on sleep" cannot.
> 
> Sounds as if your cron jobs need some serious plugins. ;)

That Telepathy module would come in handy, yes. :)
 
> > > 	a. Do a backup.
> > > 	b. Run all those pending cron jobs with "anacron -s".
> 
> Ah, I missed anacron at the first reading of Kapil's posting.
> 
> > > Having said this, I have only partially implemented (2) and (1) is
> > > often postponed. Note that (1) tends to run into lunch and the late
> > > evening as well :-)
> > 
> > [laugh] Which creates another scheduling problem if you can't do it all
> > in one swell foop. I'm not worried about that one at all.
> 
> About how much data per time period between backups are we talking? I
> just want to get a rough estimate.

Relatively minor, I'd say. Assuming that I want to back up at least once
per week, here are the factors that go into it:

1) New packages: I'm not at a point yet where I have all the packages I
want installed, but I'm certainly past the half-way point; I'm probably
installing one or two a week now, maximum. In any case, even if I lose
those, it's just not a huge factor - I can always reinstall. Worst-case
scenario: maybe 20MB worth of changes.

2) User data: This is *the* important stuff, of course. LG-related work
in /var, changes in /home and /usr/local/... that's pretty much it. I
seriously doubt that this would exceed 10MB in any given week.

So, really, we're looking at a max of 10MB that's absolutely critical,
with another 20MB that would be nice to have but no major loss if it
doesn't happen.

Hmm. Having said that, it's clear that I can do incrementals using a
flash drive, and schedule the full backups when I'm home (say, an alarm
every Monday, ignoring those that happen on the road.) Now the question
becomes, what do I use? "dump" is... crude. "backuppc" requires a hard
drive (well, maybe. I'll have to play with it and find out.) Any other
suggestions?


-- 
* Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET *