Re: [tlug] Backup CD

[Frank Bennett <bennett@example.com>]

On Thu, Mar 21, 2002 at 10:55:17PM +0900, BOTi wrote:

> About two weeks ago a new package called mondo was added to debian. I
> gave it a try and it seems to be very similar to your backup method used
> in RepliCoaster. It can back up almost any kind of filesystem to
> multiple cds (or any other media), creates a bootable cd according to
> ones setup using the kernel image and can restore to different fs types
> and partitions.

Thanks for the reference!  (Great minds really __do__ think alike ...)

I had a quick look through the mondo docs, and will spend more time studying
the system.  Mondo and RepliCoaster identify the same problem in the state of
the art (i.e. hassle-full restores) and solve it in similar ways.  Neat.

A couple of notes on the differences.  Mondo is meant for use by technical
staff, while RepliCoaster is meant to offer a largely automated interface for
use by office staff (the idea being that they are in more plentiful supply,
while the technical folks have technical things to occupy their time).  For
example, to get Mondo running, your system needs to satisfy a number of
preconditions relating to available utilities, kernel capabilities, and the
content of /etc/fstab (more to the point, it needs to __have__ /etc/fstab, as
well as a full Linux installation).  To get RepliCoaster running, you boot the
system with it, and, er, that's it (assuming that it works, of course ...).

Mondo provides wrappers for a large variety of operations, but as far as the
backup method is concerned, the two systems adopt the same approach: copying
logical files into some form of archive storage (using cpio in RepliCoaster,
and using afio in Mondo).  As noted in the Mondo docs at
http://www.microwerks.net/~hugo/download/right.html, this puts a big load on
your CPU and the IO chain leading to and including your disk; and this can
overheat your computer if its cooling system is not built to handle the
strain.  Partimage is attractive because it would reduce this burden for
fundamental backups, by snarfing the data at a lower level.

Another difference worth noting is that RepliCoaster works on sleeping
(unmounted or unaccessed) partitions. This is not true of Mondo.  From section
"VI. BACKUP" in the Mondo docs:

  Shut down all possible applications; this minimizes any compare
  differences following the backup.

In other words, Mondo backs up your data while the root filesystem is live and
{rw}, which is not perfectly safe.  You're probably okay with this approach,
but when you have suffered one disaster, it's nice to know that your backup
system is proof against further possible disasters, however unlikely.

> I looked at the Partition Image website, it sounds promising too, but I
> still believe that mondo would do a better job considering the features
> it has.

Note the comment on overheating, above.  Partimage looks to be a better
solution for fundamental backups than the afio/cpio/tar range of tools because
it uses system resources more efficiently.  Features can follow after the
bottom layer of engineering is in place.

Cheers,
Frank Bennett
Nagoya