[Dirvish] Archiving Dirvish backups

Petcher, Daniel danielp at audioprecision.com
Sun Nov 11 00:54:16 UTC 2007

I do nightly backups of a dozen servers with Dirvish onto a 1.9TB array.
Once weekly, I fetch a stack of hard drives, plug them into a RAID cabinet,
mount this 1.6 TB array and manually Dirvish my last good daily Dirvish
trees onto vaults I've created on the offsite volume. This has worked well,
but I'm about to hit a wall with regard to disk space on my offsite volume:
It has one historical dataset from two years ago, a second historical
dataset from last year, last week's backup, and this week's backup.

In order to make room for next week's backup, I will have to delete last
week's backup. I've been doing this reluctantly for a couple of months. In
effect, this is leaving me with *MORE* useful historical data in my daily
backup vaults than my offsite, unless someone requests really ancient data.
I've bought a Dell PowerVault 124T (16-slot autoloader wrapped around an IBM
Ultrium-TD3 LTO-3 tape drive). I hope to convert the offsite volume into
more space for daily backups and TAR a daily backup onto tape once weekly.
Once that's working, I can do Grandfather-father-son rotation among my
archive tapes to keep a broad recovery horizon.

Why am I asking for help among the Dirvish community? I'm getting to

I've recorded my TAR command's stdout and stderr to two log files for
analysis and I see that just a couple of the files have given an error:

Tar: {filename}: file changed as we read it

One of the files is an 11 GB tar.bz2 file and the other one is a mere 15 MB
photoshop .psd file, but I've got plenty of other huge files that haven't
failed me.

Is there any chance that my daily Dirvish backup might be getting in the way
here? Does Dirvish's backup process modify the last-accessed time of a file
when it checks to see if there have been any changes? If Dirvish needs to
make a new file instance for today's backup due to a file having changed, is
there any chance of tar misunderstanding the old file?

I've got a separate problem with my tar --compare process stopping before it
gets to the second tape, but I'm asking for help on that issue elsewhere.


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