Installing the HP C1533A drive. ------------------------------- 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 ------------------------- 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. __ ------------------------------------------------------------------ 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 -------------------------------------------------------------------