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| If you use a DAT tape you should have it checked at least every 12 months ! |
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A lot of users lull themselves into a false sense of security. They think that regular back up storing is sufficient. However, this is not the case. Tape drives may fall out of alignment, which means that the recording track has changed and is in a different position when it writes to the tape. The drop-out rate of the tape steadily increases as well. If you are interested in a technical understanding of de-alignment or drop-out, you may get detailed Information in our SPECIAL TAPE DRIVE REPORT (PDF file)....
It is important that you regularly check the condition of your tape drive. To do this, set up a directory on your hard drive with the name TEST. Copy 5 - 10 MB of files (programs, text documents, etc.) to this new directory.
Always back up this directory along with any backups you make. To start, back up this special directory to two new tapes. Name the tapes MASTER TAPE 1 and MASTER TAPE 2.
When it is possible, on a weekend day use a tape from the previous week to backup your Test directory back to your hard drive.
For example, if you made a complete data backup on 07-01-99, then use this tape to save your TEST directory back to your hard drive a week later, on 07-08-99.
If this process works then you can be sure that since the previous week, the drive did not fall out of alignment. Now, for further security you can have another Master Tape read back. But remember, that the Master Tapes are never to be written over. These tapes function only as backups. This way, you can always check if your tape drive has fallen out of alignment since setting up the Master Tapes. Please always use only Master Tape 1. Master Tape 2 should only be used to check if the drive has fallen out of alignment if you have a problem with Master Tape 1 (e.g. it has broken down due to frequent use).
If you are using several drives, then you can also rotate the tapes. This way you will be absolutely sure that each of your drives can read each of your tapes.
It is important that you stop backing up tapes when the drive doesn't read the previous tapes anymore. Recordings made with de-aligned drives must be reconstructed later in the lab. Depending on how extreme the de-alignment is, a 100% backup will be, to some extent, not possible anymore.
The costs and time needed for the reconstruction of a tape, if this should still be possible, is considerably more than following the above described prevention check. |
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