John Hudak wrote at about 12:06:29 -0500 on Saturday, February 13, 2010:
 > Hello:
 > I am considering using an external USB drive as the storage for my backups.
 > I am running backup pc under Debian 5.0.
External USB drives are a *BAD* idea for multiple reasons:
- Slow
- Unreliable
- Subject to being disconnected
etc.

 > Part 1
 > What do I need to do to configure the USB disk as the target? (e.g. how do I
 > do it?)
 > The USB disk is currently formatted as a NTFS file system.  Do I *need* to
 > reformat it to ext3? or other?
- NTFS is not usually used - need to check whether it supports the
types of hard links required for BackupPC

 > 
 > Part 2
 > Assume I am crazy paranoid about preserving backup data and I get a second
 > USB drive to serve as a backup to the first USB drive.
 > Also assume that I am not concerned about the bandwidth across the network
 > or the various buses.
 > 
 > >From a data reliability standpoint, is it better to run a backup session to
 > USB drive 1, and then repeat the backup to USB drive 2? OR
 > run a backup session to USB drive 1, and then copy the backup directories to
 > USB drive 2???
Look at the archives and FAQ - this has been discussed *many* times so
no point in wasting peoples time in rehashing.

 > The first approach could have errors in different backed up files on disk 1
 > or 2 but given the odds, very unlikely that the same exact error would show
 > up
 > in the same exact way in the same file across both USB disks.
 > OTOH, the second approach would allow the exact error in the backup on USB
 > disk 1 to be copied to USB disk 2.
 > 
 > I am leaning towards repeating the backup on two drives.
 > 
 > My understanding is that files that are backed up (using either rsync or
 > smb) are 'encrypted' (for lack of a better word), and to view them I need to
 > use zcat.-True?

There is a better word -- *compressed*

 > Also, can the backup profile be specified to perform complete data copies
 > periodically, as opposed to a baseline and then periodic incrementals?

Read the documentation and FAQ.

 > Lastly, does anyone have a statistical number that represents the
 > probability of a backup file (e.g. on the target backup disk) containing an
 > error introduced
 > by the backup procedure?  I know there are error probabilities for both disk
 > and tape reads/writes failures, but am wondering if anything like that
 > exists for the backup software.  (A group I used to work with did this sort
 > of testing, and actually had some statistics on the reliability of backup
 > programs, wrt types of files, sizes, w/wo compression, and the types of
 > compression.   Not sure the open source community would go through this type
 > of assessment - but thought I'd ask.

The probability is either 0 if no bugs in the software (or your
configuration of it) or 100% if bugs in the software and your dataset
triggers the bug. Your question is not very well-framed and pretty
meaningless. I suggest you learn a bit more about backup in general
and backuppc in particular. There is a lot of good documentation on
BackupPC in the Wikki and in the archives, I suggest you reference it...

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