SUMMARY: How to get more than 2.3 Gb on an Exabyte 8505

From: Roberto Dominijanni (
Date: Sun Aug 25 1996 - 13:35:17 CDT

ORIGINAL QUESTION: On a Sparc 2 running SunOS 4.1.3, how do I write more than
                   2.3 Gb to an Exabyte 8505?
                   After rebuilding the kernel and rebooting, the drive is
                   identified correctly ... but when I do a dump it always ends
                   with a tape error after about 2.3 Gb.

QUICK SOLUTION: I was dumping to /dev/nrst1. Dumping to /dev/nrst9 instead
                   did the trick.


Quoting from Martin Oksnevad's reply:

    Assuming your kernel has the following density settings :
          { 0x14, 0x15, 0x90, 0x8C }, /* Density selection set low to high */

    Then you use the following :
          /dev/rst1 or /dev/nrst1 to get 2.3gb
          /dev/rst9 or /dev/nrst9 to get 5.0gb
          /dev/rst17 or /dev/nrst17 to get 2.3gb compressed
          /dev/rst25 or /dev/nrst25 to get 5.0gb compressed

    In SunOS 4.1.* you can define up to 8 tape drives ie. rst0-7.
    All these tape drives can have up to 4 density settings (rstX + Y*8)
    where X is 0-7 and Y is 0-3.

This was the key piece of information I was missing. To complete the
picture, ther kernel mods I used were those recommended by Exabyte, that is,
I added the following lines to /sys/scsi/targets/st_conf.c,

    /* Exabyte 8mm w/compression (Half-High) */
            "Exabyte EXB-8505 8mm Half-High", 16, "EXABYTE EXB-8505",
            ST_TYPE_EXB8500, 1024,
            5000, 5000,
            { 0x14, 0x15, 0x90, 0x8C }, /* Density selection set low to high */
            { 0, 0, 0, 0 }

rebuilt and installed the kernel, and rebooted. None of the header files were
changed. The dump script was of the form

    dump 0ucdsbf 108000 68000 126 /dev/nrst9 /dev/rsd0a
    dump 0ucdsbf 108000 68000 126 /dev/nrst9 /dev/rsd0g
    mt -f /dev/rst1 rewind


    Marcel Chukwunenye (
    Martin Oksnevad (
    Adolfo Vaal Neto (
    Jeff Wasilko (

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