On Wed, 2004-09-15 at 17:45, James Wilkinson wrote: > Jeff Vian wrote: > > Be careful. AFAIK using the dd command to copy to a tape may overwrite > > the tape formatting. This will not be nice if it makes the tape > > unusable. > > > > The OP said he used tar to create the tapes. Why not use tar to copy > > tape to tape? (and avoid potential problems with formatting of the tape) > > This is good advice: use tar to check the consistency of the tapes. > > The one thing that's been worrying me about this entire conversation is > the possibility of data loss. It seems to me too likely that there is > something about these tapes (or drives) of which we aren't aware, and > that two or ten years down the line, the tapes are found to be > unreadable because of problems now. > He made one other statement that follows with this thought. He said he had put 18 images on the first tape. Unless he did that by creating a single tar image he would have had to use a non-rewinding feature of the tape drive (and thus 18 separate tar images), and would have to position it to each image for the extract. > Tapes tend to be used for backups, which means that people tend to just > use them for at most three purposes: backing up, restoring, and if > you're lucky, some way of doing a basic integrity test [1]. > > But that means that if you're doing anything more, you're stepping > outside the boundaries of most people's experience with tapes. > > I'm sure the OP will be very aware of the need to check *all* the tapes > he writes, and to make sure he can retrieve all the files. But I'm > paranoid, and think you can't stress such concerns highly enough. > > James. > > [1] For example, at work, my backup scripts have an option to read the > contents from the tape. Both tar and cpio have to re-read the entire > archive to produce this, so I can be pretty sure that the entire > archive is readable. > > -- > E-mail address: james | 'Short for "Sic Transit Gloria Humanorum", which is > @westexe.demon.co.uk | Latin for "There goes the neighbourhood!"' > | -- Menno Willemse >
