tape backup from remote

[Christoph Sold]

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On Monday 29 March 2004 20:33, Sean Ellis wrote:
> Hello,

G'day,

> I have a very general question about backing up to tape from a remote
> computer. The tape drive is unfamiliar territory for me, and I'm
> looking for recommendations for a sequence of steps to take.

Wise decision.

> Both machines are running fbsd 4.*, the local machine is a recent 4.9
> STABLE, and the tape drive is a Conner CTD800R-S. Will it be
> possible, or advisable, to use a utility to back up over the net
> directly to the tape, or should we be creating a local mirror and
> backing up this?

Backing up remotely can yield _very_ unsatisfying results for several 
reasons:
- - If there is not enough bandwith, the tape "trashes": After backing up 
a few blocks, the tape has to stop, rewind, then re-synchronize and 
append to the previously written data. This is _much_ slower than 
nominal backup speed.
- - If the network latency is too high, the backup software may get 
confused and abort.
- - If the connection is dropped during backup, may tools invalidate the 
whole backup.

There are both commercial as well as open source tools dealing with this 
situation. I used amanda (in the ports) to backup multiple remote 
clients to one backup machine. Never experienced any data loss during 
restore.

> I know that these are very basic questions, but I felt that posting
> here in isp might give me a more informed response. 

Have a look at http://www.thestoragegroup.com/pubs.html , the links 
there show many aspects of backup and recovery.

Another hint, though: DDS (DAT) is not up to the job. I personally 
ditched all DDS devices after multiple data loss events being caused by 
worn tapes, never properly written tapes, over-aged tapes. Never 
happend with DLT, though.

HTH
- -Christoph Sold
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