Installing the HP C1533A drive.
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The C1533A drive is a standard SCSI 2 device which operates on single-ended
narrow SCSI busses. It supports synchronous SCSI and data phase disconnect.
It can use the Media Recognition System, is capable of reading and writing
both DDS1 and DDS2 and supports data compression.
Option switches
---------------
I am grateful to Neil Long of Oxford University for providing me with
details of the option switch settings.
There is a set of 8 option switches on the underside of the C1533A. These
control various aspects of the drives interface.
Switches 1 and 2 control the default compression mode. With both switches
on compression is enabled at power on with host control. This is the
recommended setting. To disable compression turn switch 1 off.
According to the manuals switch 3 controls MRS, but other information I
have received contradicts this, and test I have performed support the
other information rather than the manuals.
The switches to not each control one aspect of the drive as "toggles".
Rather, the 6 switches allow 64 different configuration options. The most
suitable for SGI is to have 3,6,7,8 off and 1,2,4,5 on. This setting has
the following consequences:
MRS off
parity on
no data phase disconnect
MRS is best left off (at least I think so) since it enables writing to
non-MRS tapes, and loading should be quicker because the drive doesn't have
to read the MRS tape header. If you want to use MRS then turn on switch 8
(but leave the rest the same).
Data phase disconnect is disabled because IRIX requires disconnect on
32 bit boundaries, but the drive can disconnect on 16 bit boundaries. This
causes a "disconnected on non-word boundary ... Resetting SCSI bus" error,
and the bus is reset upsetting everything attached to the bus. If disconnect
is disabled and the drive is on the same bus as other devices they will
not be able to be accessed whilst a command to the drive is active. Rewinding,
partitioning and other activities which take a long time will hang the bus and
may cause serious problems if the drive is on the same bus as the system disk.
Whether there is any way to reliably make the drive work in disconnect mode
I dont know. If you want to risk data phase disconnect then switch 3 should
be on.
To sum up
1 2 3 4 5 6 7 8
Cmpr On, MRS off, DPD off On On Off On On Off Off Off
Cmpr On, MRS on, DPD off On On Off On On Off Off On
Cmpr On, MRS off, DPD on On On On On On Off Off Off
Cmpr On, MRS on, DPD on On On On On On Off Off On
Cmpr Off, MRS off, DPD off Off On Off On On Off Off Off
Cmpr Off, MRS on, DPD off Off On Off On On Off Off On
Cmpr Off, MRS off, DPD on Off On On On On Off Off Off
Cmpr Off, MRS on, DPD on Off On On On On Off Off On
/var/sysgen/master.d/scsi
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Add the following entry to the /var/sysgen/master.d/scsi so the system
will recognize the device as a DAT drive.
After this do an autoconfig and reboot to use the new kernel.
The default block size is set to 32k, so utilities like tar which use
this will keep transfers short so as not to tie up the bus for long
periods.
{ DATTAPE, TPDAT, 2, 6, "HP", "C1533A", 0, 0, {0, 0, 0, 0},
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 },
Controlling the drive
---------------------
With compression under host control it ought to be possible to switch it on
and off via the computer. Unforunately there is no support in IRIX to do this.
Also, the drive keeps all sorts of useful information in LOG and MODE SENSE
pages. From these pages you can find out what compression ratio the drive
is managing, how much space is left on the tape, what the read/write error
rate is, what size partitions there are on the tape and some other, not quite
so useful bits and pieces.
To acces these facilities I have written a set of programs. These are availble
using anonymous ftp from ion.le.ac.uk (143.210.44.97) in the directory
/HP_C1533A.
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Nigel Wade | E-mail : nmw@ion.le.ac.uk
System Administrator |
Ionospheric Physics Group | phone : +44 (0)116 2523568
University of Leicester |
Leicester, LE1 7RH, UK | fax. : +44 (0)116 2523555
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