6/26/95 -- HP Dat Drive Installation Information on SGI IRIX systems

OVERVIEW

IRIX supports all compression modes and block options for the HP 1533 and 35480A series of drives.  It also can use the 35470A, which does not support compression.  In order to use these features it is necessary to define the hp device in the SGI kernel, as well as making special device files in /dev.

PROCEDURE

Peform all the following steps as root.

1.	Modify the "scsi" file, adding a definition for the hp dat drive.
	    In IRIX 5.1 or earlier this is the file:
		/usr/sysgen/master.d/tpsc
	    In IRIX 5.2 and IRIX 5.3 this is the file:
		/var/sysgen/master.d/scsi

Copy your scsi file to a backup, e.g. scsi.original.
		# cd /var/sysgen/master.d 
		# cp -p scsi scsi.original

Open the scsi file as root with your favorite editor.  You will notice it is composed of sets of entries enclosed in {}'s.  These entries define a mapping between device names and their capabilities.

One new entry will be needed for each different type of DAT drive attached to your system.  In the example below, adding an HP C1533 is shown.  For other HP DAT drives, you can determine the name of the device by running the mt status command (among other status information, the name is displayed as two strings, seperated by a ":", e.g. HP:C1533A).

Search for the "Python" entry, make a copy and insert it just above the "Python" entry. Modify the copy as follows:

For an HP 1533, change the first line of the entry:  
    { DATTAPE, TPDAT, 7, 6, "ARCHIVE", "Python", 0, 0, {0, 0, 0, 0},
to
    { DATTAPE, TPDAT, 2, 6, "HP", "C1533A", 0, 0, {0, 3, 3, 3},

For an HP 35470A, change the first line of the entry:  
    { DATTAPE, TPDAT, 7, 6, "ARCHIVE", "Python", 0, 0, {0, 0, 0, 0},
to
    { DATTAPE, TPDAT, 2, 8, "HP", "HP35470A", 0, 0, {0, 0, 0, 0},

For an HP 35480A, change the first line of the entry:  
    { DATTAPE, TPDAT, 7, 6, "ARCHIVE", "Python", 0, 0, {0, 0, 0, 0},
to
    { DATTAPE, TPDAT, 2, 8, "HP", "HP35480A", 0, 0, {0, 3, 3, 3},

The two numbers (2 and 8) between "TPDAT" and "HP" are string lengths corresponding to "HP" and "HP35480A".

Remove the MTCAN_AUDIO attribute.
    MTCAN_SILI|MTCAN_AUDIO|MTCAN_SEEK|MTCAN_CHTYPEANY,

Change
    40, 4*60, 4*60, 5*60, 512, 512*512 },
to
    40, 4*60, 4*60, 5*60, 512, 64*512 },

The net result will look like this (an HP 1533 is shown):

    { DATTAPE, TPDAT, 2, 6, "HP", "C1533A", 0, 0, {0, 3, 3, 3},
    MTCAN_BSF|MTCAN_BSR|MTCAN_APPEND|MTCAN_SETMK|MTCAN_PART|MTCAN_PREV|
    MTCAN_SYNC|MTCAN_SPEOD|MTCAN_CHKRDY|MTCAN_VAR|MTCAN_SETSZ|
    MTCAN_SILI|MTCAN_SEEK|MTCAN_CHTYPEANY,
    /* minimum delay on i/o is 4 minutes, because when a retry is
    * performed, the drive retries a number of times, and then
    * rewinds to BOT, repositions, and tries again.  */
    40, 4*60, 4*60, 5*60, 512, 64*512 },

2.	Remove tape devices (they will be regenerated automatically):

# /bin/rm /dev/rmt/*
# /bin/rm /dev/tape
# /bin/rm /dev/nrtape

3.	Recompile the kernel using autoconfig.  

# autoconfig

If you get any error messages at this step, check the HP entry you made in the scsi file.  

4.	Reboot.


OTHER NOTES
	
If you need to exchange tapes with systems that use other DAT drives, you will find that they can always read your tapes but you may have difficulty reading their tar tapes.  The reason is that SGI by default uses a block size which is too large for the hp to deal with directly.  To read such a tar tape, use this command:

	% dd if=/dev/tape ibs=512k obs=20k | tar xvf -

If you are having difficulty reading a tape produced by another HP DAT drive, make sure your drive and the source drive are compatable.  For example, 120m media can only be used by the HP 1533.  

			no compression	|	compression
			60m	90m	120m	|	60m	90m	120m
C1533A	r/w	r/w	r/w		|	r/w	r/w	r/w
35480A	r/w	r/w			|	r/w	r/w
35470A	r/w	r/w			|

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