ArGest Backup User Guide

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Appending to Existing Archives

Tape drives allow you to write several archives, or filesets on a single tape. To do this, you must prevent the tape from performing a rewind after it has completed writing (the normal mode of operation). This can be accomplished by using the norewind device node. When the norewind device is used, BRU will begin to write data at the current tape position and will stop the tape, without rewinding, when the backup has completed. Be aware that when the norewind device is used, it is impossible to rewind the tape and BRU’s automatic verification features will be disabled.

If you use the norewind device, you must position the tape at the proper file mark before attempting to read or write. Tape utilities that do this are normally furnished with your UNIX system (or can be furnished by your tape drive vendor). The names of these tape utilities vary widely, but common names are: tape, tapecntl and mt. Refer to your system documentation for specific details. NOTE: You should not attempt to store multiple archives on a single tape unless you have very good reasons for doing so. Do not do it simply to save on tape costs.

Many newer tape drives can handle several Gigabytes and it may seem appealing to have the capacity to store a week’s worth of backups on a single tape. Do this, and you’re “putting all your eggs in one basket.” You could lose all your backup data if your tape is damaged. The cost of a few more tapes will seem cheap compared to the trouble you’ll have trying to restore (or re-create) your data.