Thursday, January 19, 2006

Ask the Engineer

We get asked this question a lot in relation to NetApp Filers

DUMPING TO MULTIPLE TAPES IN AN AUTOLOADER

Question: Is there a way to get NetApp's standard dump command to automatically sequence through tapes in an autoloader? Or do I still have to manually break things up per tape?

Answer: Find out if your autoloader or tape library supports "Stacker Mode" or "Sequential Mode". Spectra Logic 2K TreeFrogs, for instance, support the former. Your manual can explain how to set it.

The autoloader in Stacker or Sequential Mode is dumb, only knowing that if a tape is ejected then it should remove the tape and replace it with the next one in line.

Once the Library is in Stacker or Sequential Mode, then you just need to specify, in the DUMP command, the drive name for each required tape.

EXAMPLE 1: To dump a volume named "test" to tape you could use:

    dump 0f urst1h /vol/test

    urst1h is the device name on a sample tape library and passes the commands for unload rewind. Run sysconfig -t to determine the equivalent for your own autoloader tape library.

EXAMPLE 2: Now lets say your volume is 150GB and your tapes hold 50GB each uncompressed. You would need 3 tapes. The command to span the three tapes using DUMP would be:
    dump 0f urst1h,urst1h,urst1h /vol/test
In the above example, the number of tapes is indicated in the command line. If the filer does not complete the dump in the specified number of tapes and needs more, then it will drop you out to the filer prompt with a device open error. This indicates that the tape library is not ready, but that the filer wants to continue the dump.

To continue, you simply need to make sure another tape is available in the library, and then type yes [ENTER] to retry. The dump will continue with the next tape.

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