The question was :
>It seems that the question was aked last year but I didn't find any answer.
>
>I want to connect a HP C1553A DDS-2 Tape Drive to a DEC 3000/300L.
>
>Is it possible to control (or to decide ) the compression by software, i.e. by
>choosing /dev/rmtxh instead of /dev/rmtxm , or do I have to configure the
>switches with "Compression enabled at power on,no host control"
--- alan_at_nabeth.cxo.dec.com (Alan Rollow - Dr. File System's Home for Wayward Inodes.)
If the drive has a way of enabling compression via software, then
it should be possible on Digital UNIX. In /sys/data is a file
called cam_data.c. This user customizable source that is fairly
well commented. It contains the device recognition tables for
the SCSI driver and for tapes includes the ability to specify
density selection.
Depending on how much the HP resembles the 4mm tape we sell as
the TLZ07, it should be possible to adapt the TLZ07 entry to
do the right thing for the HP. And even if notably different
it will provide a guide for how that sort of thing is done.
----- Andrew Greer <Andrew.Greer_at_vuw.ac.nz>
I tried it using our C1553A on a DEC 3000/300LX and if you used /dev/rmtxl
you got no compression and /dev/rmtxh compressions was turned on (the DC showed
up). So I take that to mean yes.
----------
So I've looked at /sys/data/cam_data.c and as Alan said is a very well commented
source file (good example for programmers).
I've created an entry for the HP reader which resembles to the TLZ06 :
< /* HP C1533A - RDAT drive */
< {"HP C1533A", 14, DEV_TZRDAT, (ALL_DTYPE_SEQUENTIAL << DTYPE_SHFT) | SZ_,
< (struct pt_info *)ccmn_null_sizes, SZ_NO_BLK, (DEC_MAX_REC - 1),
< &tlz06_dens, NO_MODE_TAB, SZ_NO_FLAGS,
< NO_OPT_CMDS, SZ_READY_DEF, SZ_NO_QUE, DD_REQSNS_VAL | DD_INQ_VAL,
< 36, 64
< },
Then I regenerated the system and i've got a new vmunix file which is exactly
the same size as before. I'm a little puzzled by this.
When I issue a mt status command, the answer is with the TZRDAT name. Then I've
used a DDS 90m tape and done a dd if=/dev/rrzxc of=/dev/rmt0h. The result is
that tape ends after approximately 2Gb, so it seems that no compression was
done. I have no DC light on my drive so it doesn't show up. But perharps it's
not possible to compress with dd.
Several questions
- Did I forget something ? Or modifying cam_data.c, regenrating a system and
rebooting is enough ?
- am I using the right tapes ?
- When I look at the rmt0* files in the /dev directory, the minor numbers
are not 0,1,2,3,4,5,6,7 but 0,2,4,6 for l, h, m and a. The four others
are for nrmt0*. So is it compatible with the decsriptions in cam_data.c ?
Thank you,
Daniel
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Received on Wed Oct 04 1995 - 10:45:09 NZDT