.\" Copyright (c) 1990 The Regents of the University of California. .\" All rights reserved. .\" .\" This code is derived from software contributed to Berkeley by .\" the Systems Programming Group of the University of Utah Computer .\" Science Department. .\" .\" Redistribution and use in source and binary forms are permitted provided .\" that: (1) source distributions retain this entire copyright notice and .\" comment, and (2) distributions including binaries display the following .\" acknowledgement: ``This product includes software developed by the .\" University of California, Berkeley and its contributors'' in the .\" documentation or other materials provided with the distribution and in .\" all advertising materials mentioning features or use of this software. .\" Neither the name of the University nor the names of its contributors may .\" be used to endorse or promote products derived from this software without .\" specific prior written permission. .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED .\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. .\" .\" @(#)st.4 5.1 (Berkeley) 6/29/90 .\" .TH ST 4 "June 29, 1990" .UC 7 .SH NAME st \- CCS SCSI tape driver .SH SYNOPSIS .B "tape st0 at scsi? slave ?" .SH DESCRIPTION The .I st driver was written especially to support the Exabyte EXB-8200 8MM Cartridge Tape Subsystem. It has several extensions specific to the Exabyte, but should support other tape drives as long has they follow the ANSI SCSI-I specification. Besides extensive use with an Exabyte, the driver has been tested with an Archive QIC-24 tape drive. The .I st tape interface provides a standard tape drive interface as described in .IR mtio (4) with the following exceptions: .TP 3 1. Density is dependent on device type. Current Exabyte hardware has only one density. The EXB-8500 drive, when released, will have a high density format of 5.6GB. On an Archive QIC-24 drive the driver reads both QIC-11 and QIC-24 formats but writes only QIC-24. .TP 3 2. Only the ``raw'' interface is supported. .PP Special Exabyte Support: The MTIOCGET ioctl call on an Exabyte returns this structure: .nf struct mtget { short mt_type; /* type of magtape device */ short mt_dsreg; /* sc_flags */ short mt_erreg; /* high 8 bytes error status */ /* low 8 bytes percentage of Rewrites if writing, ECC errors if reading */ short mt_resid; /* Mbyte until end of tape */ }; .fi Bit 4 in the minor device number is used to select long filemarks or short filemarks. A long filemark occupies 2.12 MBytes of space on the tape, while a short filemark occupies 488 KBytes. A long filemark includes an erase gap while the short filemark does not. The tape can be positioned on the BOT side of a long filemark allowing data to be appended with a write operation. Since the short filemark does not contain an erase gap which would allow writing it is considered to be non-erasable. If either type of filemark is followed by blank tape, data may be appended on its EOT side. Bit 5 in the minor device number selects fixed block mode with a block size of 1K. Variable length records are the default if bit 5 is not set. For unit 0 here are the effects of minor device bits 2,3,4,5. For other units add the .I unit# to each of the device names. .(b M .nf norewind high density short filemarks fixed block mode rst0 nrst0 X rst8 X nrst8 X X rst16 X nrst16 X X rst24 X X nrst24 X X X rst32 X nrst32 X X rst40 X X nrst40 X X X rst48 X X nrst48 X X X rst56 X X X nrst56 X X X X .fi .)b .SH BUGS The HP 98268 SCSI controller hardware can not do odd length DMA transfers. If odd length DMA I/O is requested the driver will use the "Program Transfer Mode" of the Fujitsu MB87030 chip. Read requests are normally even length for which a DMA transfer is used. If, however, the driver detects that a odd length read has happened (when a even length was requested) it will issue the EIO error and the last byte of the read data will be 0x00. Odd length read requests must match the size of the requested data block on tape. The following only applies when using long filemarks. Short filemarks can not be overwritten. .(q .in +4 Due to the helical scan and the erase mechanism, there is a writing limitation on Exabyte drives. "tar r" or "tar u" will not work ("tar c" is ok). One can only start writing at 1) beginning of tape, 2) on the end of what was last written, 3) "front" side of a regular (long) filemark. Say you have a tape with 3 tar files on it, want to save the first file, and want to begin writing over the 2nd file. On a normal 1/4" or 1/2" drive you would do: "mt fsf 1; tar cf /dev/nrst0 ..." but for an Exabyte you need to do: "mt fsf 1; mt bsf 1; mt weof 1; tar cf /dev/nrst0 ..." The regular long filemark consists of an erased zone 3.8" long (needed to begin a write). In this case, the first filemark is rewritten in place, which creates an erased zone AFTER it, clearing the way to write more on the tape. The erase head is not helical. One can position a tape to the end of what was last written by reading until a "BLANK CHECK" error is returned. Writing can be started at this point. (This applies to both long and short filemarks.) The tape does not become positioned somewhere down the "erased" area as does a conventional magtape. One can issue multiple reads at the "BLANK CHECK" error, but the Exabyte stays positioned at the beginning of the blank area, ready to accept write commands. File skip operations do not stop at blank tape and will run into old data or run to the end of the tape, so you have to be careful not to "mt fsf too_many". .in -4 .q) Archive support gets confused if asked to moved more filemarks than there are on the tape. This man page needs some work. Some of these are not really bugs, just unavoidable consequences of the hardware. .SH "SEE ALSO" mt(1), tar(1), mtio(4), .I "EXB-8200 8MM Cartridge Tape Subsystem Interface User Manual."