backup

[Mikkel L. Ellertson]

Cameron Simpson wrote:
> On 19Mar2008 17:24, Tom Holroyd <tomh at kurage.nimh.nih.gov> wrote:
> | Show of hands: compress backups? Or 1:1 copy.
> 
> My choice? No per file compression. Let the storage substrate compress if
> possible - eg modern tape drives do it on their own. Or if it doesn't, you
> might compress the "archive of everything" file (eg a tar or dump file).
> Otherwise you have to do "special" stuff on restore; it's untidy. 
> 
> This position is a gross simplification of things of course.
> 
> Example: there are systems I backup with rsync to a new hardlinked tree from
> yesterday's snapshot. Obviously this is 1:1, with incremental cost.  It goes
> to tape from an uncompressed tar file because the tape drive does some
> compression.
If the storage device does not do compression, then from a 
reliability standpoint, you are better off with per file compression 
as opposed to total backup compression. The reason for this is that 
if a compressed file gets corrupted, you lose that file, but if a 
compressed back gets corrupted, you have a hard time recovering the 
files after the corruption.

Mikkel
-- 

   Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

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