Archiving Data to Tape

The following is a brief description of the steps involved in writing files to tape, e.g. for archiving. There are tape drives on riot and blast, accessible via the following device names. Check the lab map for machine locations.

riot:/dev/tape

blast:/dev/rmt/0cn

If you are archiving from dodo, please follow the instructions from this page.

Examples of the following steps are given for each machine.

Steps

Insert the Tape

The lab currently stocks tapes in two sizes: DC4-90 and DC4-120. DC4-90 tapes hold approx. 2 Gbyte uncompressed, 4 Gbyte compressed. DC4-120 tapes hold approx. 4 Gbyte uncompressed, 8 Gbyte compressed.

Rewind the Tape

For riot:

% ssh riot mt -f /dev/tape rewind

For blast:

% ssh blast mt -f /dev/rmt/0cn rew

Advance the Tape

Fast forward the tape to the n-th end-of-file (n is a number).

% ssh riot mt -f /dev/tape fsf n

or:

% ssh blast mt -f /dev/rmt/0cn fsf n

Write to the Tape

To write directory 'dirname' and its contents to the tape:

% tar -cf - dirname | ssh riot dd of=/dev/tape

or:

% tar -cf - dirname | ssh blast dd of=/dev/rmt/0cn

Read the Table of Contents

To read the table of contents of a tar file on the tape, first fast forward the tape to the desired file as described above. Then:

% ssh riot dd if=/dev/tape | tar -tvf -

or:

% ssh blast dd if=/dev/rmt/0cn | tar -tvf -

Retrieve Files from the Tape

To retrieve files from the tape, first fast forward to the desired tar file as described above. Then:

% ssh riot dd if=/dev/tape | tar -xvf -

or:

% ssh blast dd if=/dev/rmt/0cn | tar -xvf -

Using Compression

Files can be compressed by using the -z option to tar. Compressed files must also be read using the -z option. Example for riot: Write:

% tar -czf - dirname | ssh riot dd of=/dev/tape

Read:

% ssh riot dd if=/dev/tape | tar -tvzf -

Other Notes

Tar can be made verbose using the -v option.
Increase speed by increasing block sizes. Insert bs=126k after dd in both write and read commands. Remember to write the block size (126k) on the tape label for later reference.
For long archives, redirect verbose output to a file and run in the background. Surround the entire command with parenthesis, then append:
```
>& result_filename &
```

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Last modified: Wed Mar 18 14:48:00 PST