[UFO Chicago] Comcast Cuts Off Bandwidth Hogs

[Jesse Becker]

--- "Neil R. Ormos" <ormos at ripco.com> wrote:
> There are some interesting incremental backup
> strategies involving rsync and symlinks [1], but
> they usually invert what is ordinarily expected in
> terms of which backup is "complete" and which
> backup is "incremental".  The latest backup is

Beg pardon, but I think you mean 'hard links', and not
symlinks. :-)

The idea is along these lines:

Day 0:  Copy all files from the source to the backup
filesystem.  Call this backup 0.

Day 1:  Clone the directory tree on the backup FS using
hard links (the -l option to 'cp').  This doesn't consume
any additional disk space (although it will take twice the
inodes...).  Run rsync against this new dirtree, with
appropriate options.  Call this backup 1.

Day 2:  Clone backup 1 using cp -l.  Rsync the source
against new dir tree, etc.

Repeat as far back as you wish, and have disk space for. 
The most recent backup is always a "full backup,"
functionally speaking.

The neat trick is that unchanged files are only stored
once, but hard-linked into their correct dir structure.

See:  http://www.mikerubel.org/computers/rsync_snapshots/
and http://www.rsnapshot.org/howto/ for more info.

> "complete" and the prior backups are
> "incremental".  This arrangement works fine if you
> want to keep a complete copy of the original tree
> online, but it is not conducive to saving
> incremental backups to offline media such as tape,
> DVD, CD-ROM.

Agreed.  Additionally, it's much harder to make use of
compression with your backups.

--
Jesse Becker
GPG-fingerprint:  BD00 7AA4 4483 AFCC 82D0  2720 0083 0931 9A2B 06A2


 
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