[Beowulf] (no subject)

Mark Hahn hahn at mcmaster.ca
Fri Feb 16 14:17:57 PST 2007

> not buy a tape drive for backups.  Instead, I've got a jury-rigged backup

tapes suck.  I acknowlege that this is partly a matter of taste,
experience and history, but they really do have some undesirable properties.

> scheme.  The node that serves the home directories via NFS runs a nightly tar 
> job (through cron),
> 		root at server> tar cf home_backup.tar ./home
> 	root at server> mv home_backup.tar /data/backups/
> where /data/backups is a folder that's shared (via NFS) across the cluster. 
> The actual backup then occurs when the other machines in the cluster (via 
> cron) copy home_backup.tar to a private (root-access-only) local directory.
> 	root at client> cp /mnt/server-data/backups/home_backup.tar 
> /private_data/
> where "/mnt/server-data/backups/" is where the server's "/data/backups/" is 
> mounted, and where /private_data/ is a folder on client's local disk.

did you consider just doing something like:

 	root at client> ssh -i backupkey tar cf - /home | \
 		gzip > /private_data/home_backup.`date +%a`.gz

I find that /home contents tend to be compressible, and I particularly
like fewer "moving parts".  using single-use ssh keys is also a nice trick.

> large (~4GB).  When I try the cp command on client, only 142MB of the 4.2GB 
> is copied over (this is repeatable - not a random error, and always about 
> 142MB).

might it actually be be sizeof(tar)-2^32?  that is, someone's using a u32
for a file size or offset?  this sort of thing was pretty common years ago.
(isn't scientific linux extremely "stable" in the sense of "old versions"?)

> only some of the file be copied over?  Is there a limit on the size of files 
> which can be transferred via NFS?  There's certainly sufficient space on disk

it's certainly true that old enough NFS had 4GB problems, as well as
similar vintage user-space tools.

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