Hi Daniel,

> We're looking at the possibility of using a scsi tape drive connected to a
> NetBSD box to store long-term data and then accessing this data from a
> windows box at a later date.
> 
> So, firstly, how simple is it to either write data on the fly, or write data
> from HD, to a scsi tape drive in NetBSD?

Not hard at all.  Read the man pages for dump or pax.

> Secondly, how can this data be accessed under windows? Does windows see the
> tape drive as another drive on the system? Or do you have to copy everything
> off the tape to the HD before accessing it?

I personally don't know of backup software that interoperates between
NetBSD and Windows.  You could probably find a port of pax, but it is a
command line utility and might be more basic than you want.

Since a tape drive is not random access, most software does not treat it as
a drive with a filesystem.  Usually you use a special-purpose interface to
get the files off the tape.  Sometimes the tape has an index of the files
on it, sometimes you have to scan through the whole tape to see what files
are stored on it.  Some files can be big enough to span tapes.

Almost always you can select specific files to restore.  You usually do not
have to restore the whole filesystem at once.

> Also, if we were to access the data stored on a tape from a BSD box, would
> we have to copy the whole lot to HD first? Or can we access it from the tape
> directly?

If you are using a BSD box to store the data before it goes to tape, then
the dump command would be a good thing to consider.  The corresponding
command to get data off the tape is "restore".  The restore command gives
you a command line interface where you can change directory, get directory
listings, and flag/unflag files to be restored.  Once you are ready, you
tell it to go, and it restores the files you chose.

Depending on your purposes, it might be an option to use a drive enclosure
and just store your backups in a filesystem.  If you don't get a
hot-swappable enclosure, you'll have to shut down the system between
swapping drives.  Tapes are not significantly cheaper than IDE drives of
comparable capacity, but they do have a longer storage life and can be more
resistant to certain environmental factors such as accidentally dropping
them.

Ben