Keck Tape Backup

These instructions tell you how to put your data onto tape either at Keck headquarters in Waimea or at the summit.

Headquarters (Waimea)

At headquarters you have the choice of writing your data as either FITS images or as a Unix tar file.

Writing a tar tape

A tar tape is simpler and faster to write than a FITS tape; however, it's difficult to unload a single image from the tar tape and so is less convenient for later use. Follow these steps to write a tarfile:

Load a tape into an available drive. Currently there are Exabyte drives on hosts manele and poipu in Remote Ops II, and on pupukea and mokulau in Remote Ops I. Use only data-grade Exabyte tapes!
Open a Unix window on the host machine.

By default, your account is set up to use the Exabyte drive in its lowest-density mode. This is the recommended mode for copying tapes, because it is readable by any Exabtye drive. If you wish to use one of the higher-density settings, then issue of the following commands in the Unix window:

Density	Capacity*	Command to issue
Low	3.5GB	setenv TAPE $EXABYTE_LOW
Medium	7GB	setenv TAPE $EXABYTE_MED
High	14GB	setenv TAPE $EXABYTE_HIGH
Compressed	14GB	setenv TAPE $EXABYTE_COMP

*for a 160-meter Exabyte tape

If your tape already contains tarfiles, use the following command to skip past them:
```
mt fsf N
```
where N is the number of existing tarfiles on the tape.
In the Unix window, use the cd command to go to the directory containing your data. Remember that summit data disks can be accessed using the syntax cd /s/sdataXXX.
Issue the following command to save all files in your data directory to tape:
```
tar cv .
```
Note that the trailing period is required!
If you have other directories you wish to save, then repeat the previous two commands for each directory. If you run out of tape in the middle of writing a tarfile, then eject the tape (see next step), insert a new tape, and start over with the current directory.
When the tar command completes, use the following command to eject your tape:
```
mt offline
```

Writing a FITS tape

The advantage to saving your images in FITS format is that you can easily unload single images for later processing. However, the process of writing the tape takes longer and requires running IRAF. Follow these steps to write a FITS file using the IRAF fitscopy task:

Load a tape into an available drive. Currently there are Exabyte drives on hosts manele and poipu in Remote Ops II, and on pupukea and mokulau in Remote Ops I. Use only data-grade Exabyte tapes!
Open an Xgterm window on the host machine and run IRAF (using the command cd iraf ; cl)
In IRAF, issue the command tables to load the tables package.
In IRAF, use the cd command to go to your data directory. Remember that your data disk on the summit can be reached from any Keck computer by typing cd /s/sdataXXX.
Use the following IRAF command to write all FITS files in the current directory onto a new Exabyte tape:
```
fitscopy *.fits mta newtape+ blocking=10 verbose+
```
or use this command to append data to a tape:
```
fitscopy *.fits mta newtape- blocking=10 verbose+
```
If you have data stored in more than one directory, then repeat the previous two commands to store your other directories. If you fill up the tape, you should eject the current tape (see below), load a new one, and re-start the operation beginning at the file which was being written when the tape filled up.
Eject the tape by typing the following commands in IRAF:
```
rewind mta
!mt offline
```
If you previously used the IRAF allocate command to reserve the tape drive, then you must now use deallocate to release it!

Other IRAF tasks which write FITS tapes are wfits and stwfits. You can use IRAF's rfits task to read your tape from your home institution. You may want to verify your tape by using the IRAF command catfits mta 1-999 long- short+ (available from the tables package) to make a directory listing of your tape.

Summit and Hale Pohaku

Only the tar tape writing procedure is available at the summit and at HP. Here are the steps to follow:

Load a tape into the Exabyte drive (host punaluu at the summit, or host maunakea at HP). The Observing Assistant can direct you to location of the punaluu the tape drive. Use only data-grade Exabyte tapes!
Open a Unix window on the host machine.

Issue one of the following commands to select a density for your tape:

Density	Capacity*	Command to issue
Low	3.5GB	setenv TAPE /dev/nrst0
Medium	7GB	setenv TAPE /dev/nrst8
High	14GB	setenv TAPE /dev/nrst16
Compressed	14GB	setenv TAPE /dev/nrst24

*for a 160-meter Exabyte tape

If your tape already contains tarfiles, use the following command to skip past them:
```
mt fsf N
```
where N is the number of existing tarfiles on the tape.
In the Unix window, use the cd command to go to the directory containing your data. Remember that summit data disks can be accessed using the syntax cd /s/sdataXXX.
Issue the following command to save all files in your data directory to tape:
```
tar cv .
```
Note that the trailing period is required!
If you have other directories you wish to save, then repeat the previous two commands for each directory. If you run out of tape in the middle of writing a tarfile, then eject the tape (see next step), insert a new tape, and start over with the current directory.
When the tar command completes, use the following command to eject your tape:
```
mt offline
```

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Last modified: Thu Jan 11 21:50:12 HST