Re: backup compress on the fly
- To: Mike McCarty <email@example.com>
- Cc: firstname.lastname@example.org
- Subject: Re: backup compress on the fly
- From: Tony Godshall <email@example.com>
- Date: Tue, 4 Oct 2005 11:50:13 -0700
- Message-id: <20051004185013.GA29742@private>
- Reply-to: Tony Godshall <firstname.lastname@example.org>
- In-reply-to: <433D8A6D.email@example.com>
- References: <20050930114130.GA9671@benburb.demon.co.uk> <433D8A6D.firstname.lastname@example.org>
According to Mike McCarty,
> Joe Mc Cool wrote:
> >But, (now that I have installed all those lovely debian goodies), the
> >wretched tape is filling up and asking for another. (I erase the
> >tape beforehand.)
> >I really want to fit all my current data, or certainly selected dirs
> >unto one tape. Surely I should be able to compress the files before
> >they are sent to the tape. I suspect it can be done with gzip, but I am
> >not sure of the syntax. Obviously I need to get it right.
> Whether compression is advisable depends on what your goal is.
> If you are making archives, or you are backing up a system which,
> if it failed and you lost everything it would be a terrible
> disaster, then I recommend you *not* to compress your backups.
> Compressed file formats are notoriously intolerant of medium
> errors. It might be better to do subset backups each of which
> fits onto a single tape.
> # tar cvz [list of places to back up]
> The "c" means "create", the "v" is "verbose" (optional) and the "z"
> means "compress as with gzip the entire tar image".
Replace z with j if you want a .bz2 instead of a .gz (slower
but better compression)
For belt and suspenders, look at par... it's sort of a
file-level raid. i.e. it makes a set of files with ecc that
can heal some corruption (at the cost of taking more space).
so if you .bz2 compress and then carefully choose your par
settings, you can still get a net compression. that is,
assuming the contents of the drive being backed up are
highly compressible (i.e. no .avi .mpeg .jpeg .mp3 .gz .bz2