st(7) DG/UX R4.11 st(7)
NAME
st - SCSI Tape
SYNOPSIS
st(parent-bus[,id[,lun]])
DESCRIPTION
The st device driver accesses a Small Computer Systems Interface
(SCSI) tape drive device. The currently supported models, which are
all cartridge drives except where otherwise noted, are:
Model Description Tape Capacity Drive
Number Width Width
(inches)
6577 QIC-150 1/4 inch 150 MB 5.25
6677 QIC-320 1/4 inch 320,525 MB 5.25
6691 QIC-320 1/4 inch 320,525 MB 5.25
6590 helical scan 8mm 2 GB 5.25
6586 1600 bpi reel 1/2 inch varies -
6587 1600 bpi reel 1/2 inch varies -
6588 6250/1600/800 bpi reel 1/2 inch varies -
6589 6250/1600/800 bpi reel 1/2 inch varies -
6760 SCSI-2 helical scan 8mm 5 GB 5.25
6761 SCSI-2 helical scan 8mm 5 GB 5.25
61004 SCSI-2 helical scan 8mm 7 GB 5.25
6762 SCSI-2 DAT 4mm 2 GB 3.5
6885 SCSI-2 DDS-2 DAT 4mm 4 GB 3.5
6886 SCSI-2 DDS-2 DAT 4mm 4 GB 3.5
7921 SCSI-2 CLARiiON tape array 4mm varies -
61001 18-track IBM 3480 1/2 inch 200 MB -
61002 18-track IBM 3480 1/2 inch 200 MB -
To configure an st device, you must add a device name entry of the
form described above to the DG/UX system configuration file. The
parameters in a device name have the following meanings:
· The parent-bus parameter is itself a device name, representing
the SCSI bus device to which the device is attached (ncsc(0) or
dgsc(vme(1),B,6), for example). There is no default value for
this parameter; it must always be specified explicitly. See the
scsibus(7) man page for a list of SCSI bus device drivers.
· The id parameter is a hexadecimal number in the range 0 through F
which represents the SCSI ID used by the device on parent-bus.
Note that id values above 7 are possible only if the parent-bus
device supports Wide SCSI addressing. Consult your hardware
documentation to determine if it does.
· The lun parameter is a hexadecimal number in the range 0 through
7 which represents the SCSI Logical Unit Number (LUN) used by the
device within its id. The default value for lun is 0.
See rmt(7) for a description of the character special device access
method provided by st.
Model 6577 supports only fixed-length records of 512 bytes.
Attempted I/O to this model using a record size that is not a
multiple of 512 bytes will fail with an errno of EINVAL.
The other models support variable-length records up to 65,536 bytes.
Using Compression
Switching from uncompressed to compressed mode is allowed only when a
tape is at Beginning of Tape (BOT). For example, if you disable
compression for a model 6761 tape drive and then, after a write
operation, enable compression without first rewinding the tape in the
drive, you will get an error message. Switching from compressed to
uncompressed mode is allowed without restriction.
Model 6590 and 6760/6761 Tape Exchange
The Model 6590 SCSI drive supports only low density, uncompressed
data. The Model 6760/6761 SCSI-2 drives optionally support both
multiple densities and data compression. The Model 6590 drive can
access a tape that was produced in a Model 6760 or 6761 drive with
low density selected and data compression turned off. Conversely,
with low density selected and data compression turned off, the Model
6760/6761 drives can access a tape produced in a Model 6590 drive.
The Model 61004-D/61004-S drives support an extended length 160m data
cartridge which cannot be used in the 6590, or 6760/6761 drives. In
all other respects Model 61004-D/61004-S drives are fully compatible
with the model 6760/6761 drives.
To access a Model 6760/6761 drive with low density selected and data
compression turned off, use the ul or uln device nodes described
below. A tape created in this fashion can be accessed by a Model
6590 drive.
SCSI-2 Soft Error Monitoring
Soft error reporting has been added for models 6760, 6761, 6762,
6885, 6886 and 7921. The system periodically checks the soft error
rates for these models. If the rates exceed predefined limits, one
of the following messages will appear on the system console:
Tape device at st(parent-bus,id,lun) encountered a high number of
correctable (soft) errors. Please observe the suggested maintenance
schedule for the drive.
Tape device at st(parent-bus,id,lun) encountered an unacceptably high
number of correctable (soft) errors. Please clean the tape drive and
use a known good tape. If you receive this message frequently,
contact your DG service representative.
The first message is less serious than the second. If you receive
either message, try using a new tape. If the message persists, clean
the heads. If the message still persists, have the drive serviced.
FILES
Each st device creates a set of character-special device nodes when
it is configured, with pathnames of the form:
/dev/rmt/st(parent-bus,id,lun)suffix
Each suffix is a string of zero to three letters that select a number
of different access methods to the drive. Device nodes are created
only for the access methods supported by the particular drive model.
Each suffix has three components: a compression option, a density
option, and a rewind option.
For models that support data compression, c enables and u disables
compression. Absence of either letter selects the drive's default
compression mode, which is usually the uncompressed mode. However,
compression is enabled by default on models 6760, 6761, 6762 and
7921.
For models that support different densities, h selects high, m
selects medium, and l selects low density. Absence of any density
letter selects the drive's default density mode, which can usually be
set manually using a switch on the drive.
The no-rewind suffix n prevents the tape device from rewinding to
beginning of tape (BOT) when the device file is closed by a process.
Absence of this suffix letter means that the device will rewind to
BOT on every close.
The chk.devlink command is responsible for creating and maintaining
an additional "short-name" link to each device node described above.
See the chk.devlink(1M) and devlinktab(4M) man pages for details.
EXAMPLES
The following entry in a DG/UX configuration file configures a SCSI
tape drive device at Logical Unit Number 0 of SCSI ID 2 on the SCSI
bus named ncsc(1):
st(ncsc(1),2)
To access that device in uncompressed no-rewind mode, you would open
the following device node:
/dev/rmt/st(ncsc(1),2,0)un
SEE ALSO
scsibus(7), rmt(7), chk.devlink(1M), devlinktab(4M).
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