Backing up to DVDs

Bob Edwards Robert.Edwards at
Mon Nov 11 14:39:45 EST 2002

Antti.Roppola at wrote:
> We recently were quoted around that for an internal DVD-R
> (Pioneer A05).
> Bob's CD backup script would be pretty easy to change to
> support DVD. Since it's all tarr'ed up, you'd get your
> permissions being saved too. No terribly difficult to browse.
> Antti

Someone just pointed out to me that the "Bob" referred to in this message was 
probably me, but I didn't write the CD backup scripts - they came from Drake 
Dierdrich,  as far as I can recall.

Our backup system uses "rsync" (excellent code from Tridge and co.) which we 
customised, the customisation having been rolled back into rsync some years 
ago, namely the --backup-dir option.

We backup to a live disk on a remote server (in another building on campus), 
export that back (read-only) back to our staff desktops using NFS and use the 
--backup-dir option to create "reverse incrementals" of all files modified or 
deleted each (week) day. The archive directory of reverse incrementals are 
also exported back to staff desktops, as well as being tar'd and compressed 
and scp'd back to our CD-ROM burning machine for regular (weekly) archival 
onto CD-ROM (we also leave live versions on the backup server for about 2 
months or so, depending upon available disk space).

One recent enhancement to this scheme (implemented by Steven Hanley) is to 
detect all archived files that are proper sub-files of their respective 
current version (ie. all files that have been appended to, such as e-mail 
folders and log files) and to remove the old version from the archive. This 
reduces the size of the archive each day by about 40%.

Our system has been running reliably for about 3 years. The main advantages are:
  - cheaper than tape drives and tapes
  - offsite always (no need to manually move or even handle tapes)
  - almost no operator intervention required

This last point is important as any staff member can recover any (daily) 
version of a file changed or deleted over the past 2 months or so from their
desktop without operator intervention. After 2 months, files need to be 
recovered from the CD-ROMs, requiring mounting, uncompressing and untarring 
etc. the archives. Still generally easier than searching a tape.


Bob Edwards.

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