tz(4) Kernel Interfaces Manual tz(4)Name
tz - SCSI magnetic tape interface
Syntax
VAX NCR 5380:
adapter uba0 at nexus?
controller scsi0 at uba0 csr 0x200c0080 vector szintr
tape tz0 at scsi0 drive 0
VAX DEC SII:
adapter ibus0 at nexus?
controller sii0 at ibus? vector sii_intr
tape tz0 at sii0 drive 0
RISC DEC SII:
adapter ibus0 at nexus?
controller sii0 at ibus? vector sii_intr
tape tz0 at sii0 drive 0
RISC DEC KZQ:
adapter uba0 at nexus?
controller kzq0 at ibus? csr 0761300vector sii_intr
tape tz0 at kzq0 drive 0
RISC NCR ASC:
adapter ibus0 at nexus?
controller asc0 at ibus? vector ascintr
tape tz0 at asc0 drive 0
Description
The SCSI tape driver provides a standard tape drive interface as described in This is a driver for any Digital SCSI tape device.
For the TZK10 QIC format tape drive, the densities supported are QIC-24 (read only) block size of 512 byte blocks, QIC-120, and QIC-150
read/write block size of 512 byte blocks, and QIC-320 read/write block size of 1024 byte blocks. With QIC format style tapes all reads and
writes must be in multiple of the block size. This is a requirement of fixed block tape drives because record boundaries are not pre-
served. The QIC densities are selected using the following special device names:
QIC-24 Fixed block size.
QIC-120 Fixed block size.
QIC-150 Fixed block size.
QIC-320 Fixed block size.
With all fixed block tape devices a of a file to the tape must be padded out. An example of this is a of which has a size of approximately
3800 bytes.
dd if=/etc/gettytab of=/dev/rmt0h bs=10k conv=sync
or
dd if=/etc/gettytab of=/dev/rmt0l bs=512 conv=sync
The option of pads the output to block size.
This driver also supports n-buffered reads and writes to the raw tape interface (used with streaming tape drives). See for further
details.
Tape Support
TZ30, TZK50, TLZ04, TSZ05, TKZ08, TZK10
Diagnostics
All diagnostic messages are sent to the error logger subsystem.
FilesSee Alsomtio(4), nbuf(4), SCSI(4), MAKEDEV(8), uerf(8), tapex(8)
Guide to the Error Logger
tz(4)
Check Out this Related Man Page
SA(4) BSD Kernel Interfaces Manual SA(4)NAME
sa -- SCSI Sequential Access device driver
SYNOPSIS
device sa
DESCRIPTION
The sa driver provides support for all SCSI devices of the sequential access class that are attached to the system through a supported SCSI
Host Adapter. The sequential access class includes tape and other linear access devices.
A SCSI Host adapter must also be separately configured into the system before a SCSI sequential access device can be configured.
MOUNT SESSIONS
The sa driver is based around the concept of a ``mount session'', which is defined as the period between the time that a tape is mounted, and
the time when it is unmounted. Any parameters set during a mount session remain in effect for the remainder of the session or until
replaced. The tape can be unmounted, bringing the session to a close in several ways. These include:
1. Closing a `rewind device', referred to as sub-mode 00 below. An example is /dev/sa0.
2. Using the MTOFFL ioctl(2) command, reachable through the 'offline' command of mt(1).
It should be noted that tape devices are exclusive open devices, except in the case where a control mode device is opened. In the latter
case, exclusive access is only sought when needed (e.g., to set parameters).
SUB-MODES
Bits 0 and 1 of the minor number are interpreted as 'sub-modes'. The sub-modes differ in the action taken when the device is closed:
00 A close will rewind the device; if the tape has been written, then a file mark will be written before the rewind is requested. The
device is unmounted.
01 A close will leave the tape mounted. If the tape was written to, a file mark will be written. No other head positioning takes place.
Any further reads or writes will occur directly after the last read, or the written file mark.
10 A close will rewind the device. If the tape has been written, then a file mark will be written before the rewind is requested. On
completion of the rewind an unload command will be issued. The device is unmounted.
BLOCKING MODES
SCSI tapes may run in either 'variable' or 'fixed' block-size modes. Most QIC-type devices run in fixed block-size mode, where most nine-
track tapes and many new cartridge formats allow variable block-size. The difference between the two is as follows:
Variable block-size: Each write made to the device results in a single logical record written to the tape. One can never read or write part
of a record from tape (though you may request a larger block and read a smaller record); nor can one read multiple blocks. Data from a sin-
gle write is therefore read by a single read. The block size used may be any value supported by the device, the SCSI adapter and the system
(usually between 1 byte and 64 Kbytes, sometimes more).
When reading a variable record/block from the tape, the head is logically considered to be immediately after the last item read, and before
the next item after that. If the next item is a file mark, but it was never read, then the next process to read will immediately hit the
file mark and receive an end-of-file notification.
Fixed block-size: Data written by the user is passed to the tape as a succession of fixed size blocks. It may be contiguous in memory, but
it is considered to be a series of independent blocks. One may never write an amount of data that is not an exact multiple of the blocksize.
One may read and write the same data as a different set of records. In other words, blocks that were written together may be read sepa-
rately, and vice-versa.
If one requests more blocks than remain in the file, the drive will encounter the file mark. As there is some data to return (unless there
were no records before the file mark), the read will succeed, returning that data. The next read will return immediately with a value of 0.
(As above, if the file mark is never read, it remains for the next process to read if in no-rewind mode.)
FILE MARK HANDLING
The handling of file marks on write is automatic. If the user has written to the tape, and has not done a read since the last write, then a
file mark will be written to the tape when the device is closed. If a rewind is requested after a write, then the driver assumes that the
last file on the tape has been written, and ensures that there are two file marks written to the tape. The exception to this is that there
seems to be a standard (which we follow, but do not understand why) that certain types of tape do not actually write two file marks to tape,
but when read, report a `phantom' file mark when the last file is read. These devices include the QIC family of devices. (It might be that
this set of devices is the same set as that of fixed block devices. This has not been determined yet, and they are treated as separate
behaviors by the driver at this time.)
IOCTLS
The sa driver supports all of the ioctls of mtio(4).
FILES
/dev/[n][e]sa[0-9] general form:
/dev/sa0 Rewind on close
/dev/nsa0 No rewind on close
/dev/esa0 Eject on close (if capable)
/dev/sa0.ctl Control mode device (to examine state while another program is accessing the device, e.g.).
DIAGNOSTICS
None.
SEE ALSO cam(4), mt(1)AUTHORS
The sa driver was written for the CAM SCSI subsystem by Justin T. Gibbs and Kenneth Merry. Many ideas were gleaned from the st device driver
written and ported from Mach 2.5 by Julian Elischer.
The current owner of record is Matthew Jacob who has suffered too many years of breaking tape drivers.
BUGS
This driver lacks many of the hacks required to deal with older devices. Many older SCSI-1 devices may not work properly with this driver
yet.
Additionally, certain tapes (QIC tapes mostly) that were written under FreeBSD 2.X are not automatically read correctly with this driver: you
may need to explicitly set variable block mode or set to the blocksize that works best for your device in order to read tapes written under
FreeBSD 2.X.
Fine grained density and compression mode support that is bound to specific device names needs to be added.
Support for fast indexing by use of partitions is missing.
BSD June 6, 1999 BSD