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Model 3: Monthly and weekly rotation with daily backup
The backup model which offers optimum data protection uses six full backup sets (three monthly and 3
weekly), and four sets for daily partial backups. This model is recommended if you compile large quantities
of data where loss would be disastrous. It also provides the best method of securing data from software
viruses.
The four sets of tapes for daily partial backup are labeled Monday, Tuesday, Wednesday, and Thursday as in
model 2.
Three set of tapes are used in rotation for weekly full backup on Fridays. Two of these sets are stored off-
site. After a full backup is made on Friday, the set of tapes is taken off-site and exchanged for the oldest
backup set in storage. Next Friday, the backup is made using this oldest set of tapes. In this way, at any
moment, three generations of full weekly backup exist; the two most recent are off-site, the oldest is on-site
ready for the next backup.
The final three sets of tapes are used for full backup on the first working day of each month, again in
rotation. This is in addition to the usual backup that would be made that day, so the normal routine is
maintained. As with the weekly tapes, the monthly sets should be stored off-site.
The figure shows how this model works over a typical 15-week period.
Number of cartridges needed
Number of cartridges needed
The total number of cartridges needed depends on your backup routine, as described in the preceding
models. In addition to the numbers mentioned there, it is advisable to keep extra cartridges on hand, as
follows:
•
A spare set for full backup
•
A spare cartridge for use for diagnostics by your Service Engineer
•
Cartridges for file transfers
•
Cartridges for any archival storage you may require
Cartridge storage life
Tests show that data can be successfully stored on DDS cartridges for period of 10 years. You should give
each cartridge a full pass in the tape drive at least once a year to prevent sticking. Store the cartridges
according to the environmental specifications given in Chapters 2 and 3.
Head cleaning routine
Once your backup routine has been established, you should have an idea how many tapes are used each day.
Remember that HP recommends cleaning the drive's tape heads using the intervals shown in the table on
page page 2-7, or if the Clean/Attention LED is lit. Using this table, you can estimate how often the heads
will need cleaning and build the cleaning operation into the backup routine.
Operation
6 sets for full backup
4 sets for partial backup
2-9
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Troubleshooting
