tps(7M)tps(7M)NAME
tps, tpsc - SCSI tape interface
SYNOPSIS
/dev/rmt/tps*
/dev/rmt/*/lun*/c*p*
DESCRIPTION
Silicon Graphics systems support the Small Computer System Interface
(SCSI) for various tape drives, including QIC24 and QIC150 1/4"
cartridges, 9-track, 8 mm video, Ampex DIS/DST series, DLT (digital
linear tape), IBM 3590 and 3570, STK 9490 and 9840, STK SD3, Sony GY-10
and GY-2120, and DAT (digital audio tape) tape drives. Not all systems
support all tape drives. Since so many different types of devices are
supported, and not all their features can be determined directly from the
drive, a configuration table defines their capabilities. This is usually
found in the file /var/sysgen/master.d/scsi.
The special files are named according to this convention:
Parallel SCSI and FC-AL
/dev/{r}mt/tpscontrollerdID{nr}{ns}{s}{v}{.density}{c}
Fibre Channel Fabric
/dev/{r}mt/nodename/lunlun{nr}{ns}{s}{v}{.density}{c}/ccontrollerpport
Note that the Fabric device names always specify the lun, even
if it is zero.
controller is the SCSI controller number and ID is variously
known as the SCSI ID, the SCSI address, the drive address, and the unit number.
The nodename and port are used to indicate the Fibre Channel
world wide name (WWN) and the device port number. A Fibre Channel Fabric
device may have multiple special filenames. If the nodename and
lun of different filenames are the same, respectively, these
filenames represent the same physical device. Care should be taken not
to use the same device at the same time by unintentionally opening
different filenames of the same device.
The device types are:
{nr} no-rewind on close device
{ns} non-byte swapping device
{s} byte swapping device
{v} variable block size device. This feature is present on most current
generation tape drives, including those from STK, IBM, Sony, Quantum
and others.
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{stat} a special purpose device;
it can be used even when
one of the other names for the same physical device is already
opened (see below)
{.density} for 9-track tape it is one of 800, 1600,
3200, or 6250; for the Exabyte 8500 it is one of 8200 and 8500;
for DLT7000 it is one of 4000 and 7000
{c} data compression is supported for Archive Python 01931 DDS-2 DAT,
Sony SDT-9000 DDS-3 DAT, the various DLTs, IBM Magstar 3590
and IBM Magstar MP 3570, EXABYTE 8900, STK 9490 and 9840,
STK SD3, Sony GY-2120,
and Fujitsu M1016/M1017 3480 devices as shipped.
Compression is not
the same as density and should not be confused
with density. The degree to which compression increases capacity is
data dependent.
These special devices are accessible by only one program
at a time, except for the {stat} device.
Opens on the {stat} device
can block for several seconds, if another name for the same devices
is being opened or closed at the same time.
Similarly, the
MTIOCGET
ioctl on the {stat} device can block if long operations are in progress via
one of the other names for the same device.
The only operation the {stat} device supports is the
MTIOCGET
ioctl, open, and close; all other attempted operations cause the EINVAL
errno to be returned.
It never causes any tape movement of any
kind (in particular, it never tries to load the tape, even if
media is present).
Typically, if this tape drive is used as the system tape drive,
the device-specific names described above are
linked to user-friendly names in the /dev directory.
See
NOTES
below and
mtio(7)
for a description of the user-friendly names.
SPECIAL FEATURES
The different devices support a multitude of capabilities. In
particular, some support multiple densities, some support fixed block
size only, many support variable block sizes, some support multiple
speeds, some support direct transfer of audio data over the SCSI bus.
Most of these features are selected by which minor device is opened, and
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others must be set via ioctl commands. The list of capabilities that a
particular drive supports is set by the MTCAN_* bits set in the
master.d/scsi file for that drive. When a capability required for an
operation is not set, the EINVAL error code is returned for the request.
In particular, in audio mode the variable block size device must always
be used for I/O, and parameters such as the recording frequency, program
number, and so on are all part of the data stream. Additionally, when in
audio mode the rewind and seek commands return immediately. If the drive
is closed in this state, subsequent opens block until they are completed.
If the drive remains open, certain commands, such as MTIOCGET and
MTIOCAUDPOSN, can be used to determine the current position of the tape
during the seek or rewind operation; the third argument is a pointer to a
struct mtaudio. The MTAUD tape op is used to enable and disable audio
mode. The third argument is 0 to use data mode and 1 to use audio mode.
Many of the features that require ioctls can be set or changed via the
mt(1) command.
The data structures and values for these ioctls can be found in the
include file /usr/include/sys/mtio.h, which is shipped with all systems.
There are extensive comments in this file, and at this time no attempt
has been made to document most of them here or in the mtio(7) reference
page.
However, there are a few surprising return values that are mentioned
here. In particular, when using partitioned tapes (see mt setpart, or
the MTSETPART ioctl), partition 0 is the 'main' partition, which is the
final part of the tape, and partition 1 is the partition closest to BOT.
Partitioned tapes are intended primarily so that a tape directory can be
written at the beginning of the tape, without any worry of overwriting
the data portion of the tape. In addition, partitioned tapes indicate
BOT (EOT) when at beginning (end) of partition, rather than the 'real'
BOT (EOT).
Some devices support overwrite at arbitrary tape positions, while others
require that the tape be at BOT or EOD (end of data). Others allow
overwrite at any filemark (that is, 8mm from the BOT side of any
filemark). Some experimentation may be necessary to decide what your
particular drive supports; all drives support at a minimum writing at
both BOT and EOD, assuming the media isn't write protected.
TAPE MOVEMENT CRITERIA
The only time the driver ever moves a tape is when told to, with the
exceptions listed below. A command that causes tape movement is always
issued, assuming that it is a valid command and the media is loaded.
A significant change from IRIX releases prior to 4.0 is that the driver
does NOT automatically position to the next filemark on the first command
that does I/O to the tape. This means that mt bsr, and mt fsr now have
meaning since the tape is in fact left where it is positioned. It is now
the programmer's or user's responsibility to ensure that the tape is in a
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valid state for I/O. The drive or driver still detects and prevents
operations not valid for the current tape position, returning an
appropriate error in errno.
1. If the first read after an open encounters a filemark before
transferring any data and the tape was not known to be at the
top of a filemark or BOT, the filemark is skipped and the read
retried. Any further errors are reported exactly as they occur.
In particular, if two sequential filemarks are found, the tape
is positioned between them.
2. If a read command encounters a filemark, that read returns a
short count (if any data was read) or 0. If a short count is
returned, the next read returns 0, allowing detection of
filemarks. An MTFSF ioctl should not be done at this point, as
the tape drive itself has already passed over the filemark. If
an MTFSF is done at this point, the count should be decremented
by one. The driver attempts to deal with this case, but can not
always do so, due to differences in drive firmware.
The read following the read that returns 0 returns the data in
the next tape file, if any. Note that this is a change from
earlier IRIX releases, which required an explicit MTFSF or other
tape ioctl to move the tape before further reads could be done.
The new behavior is consistent with most actual tape drives and
tape drivers in most BSD-derived UNIX systems. Similarly, if an
MTFSR ioctl encounters a filemark, it stops at the filemark and
subsequent reads return data from the next tapefile, if any.
3. If early warning is encountered on a write or write filemark,
the driver does not allow further writes or write filemarks,
unless the MTANSI ioctl is issued. Any data remaining is
flushed to tape, if possible. For the QIC tape drives and the
8mm drives, an error is returned on both read and write unless
all the data was transferred when early warning is encountered.
This is so that older multi-volume backups continue to work and
new ones can be read on older releases. All newer drives (9
track, DAT, and future drive types) return a short count if not
all the data could be transferred. Requests other than read or
write are sent to the tape drive as usual.
4. On close, if the last tape movement operation was a successful
write (not a write filemark), the following happens:
a) Half-inch tape drives write two filemarks and then backspace
one file, so that the tape is positioned between the two
filemarks just written. If, however, the tape is not in
ansi mode and early warning has been encountered, no write
filemark or backspace is done; filemarks are never written
in audio mode.
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b) Other tape drives write one filemark. No backspace is done.
5. On the first status request or request that does tape motion
after a system boot, a SCSI bus reset, or a tape cartridge
insertion, the tape is rewound and loaded; this occurs even for
the norewind devices. [Note: This can be suppressed via
master.d/scsi changes (e.g. Ampex drives)]. In addition, most
drives rewind a tape when it is ejected. This means that if you
wish to append a new dataset to a tape that already contains
datasets, you should always issue the mt feom command AFTER
loading the tape, just prior to using the program that will
append to the tape. Do not count on a tape remaining at EOD,
just because that is where it was before it was removed.
For devices that support it, the prevent media removal command is
sent to the drive on open and released on close, so that eject
buttons (when present) are disabled.
ERROR RETURNS
The following errors are returned by this driver; other errors can also
be returned by higher levels of the operating system.
EAGAIN The drive returned an error indicating it was not ready (tape
ejected, drive taken offline, and so on).
EBUSY Returned on opens when the drive has already been opened.
EFAULT A bad address was passed in a call that required a data
transfer.
EINVAL This is returned for requests that are invalid for one reason
or another including:
o Attempting to write or write file-mark after reading (except
in audio mode, for devices that support it) without an
intervening close, or ioctl to re-position the tape.
o Attempting to read after writing (same exceptions as for
writing).
o Using an invalid count on read, write, write file-mark, and
so on.
o Attempting to do MTAFILE on a drive that doesn't support it
(the MTCAN_APPEND bit is not set in the master.d/scsi file).
o Attempting to do an ioctl on a drive that doesn't support it
(such as MTBSR on Cipher 540S) or attempting to do an
unsupported MTOP operation or other unsupported ioctl's.
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o Attempting to write to a QIC24 cartridge from a QIC150 drive
(an MTIOCGET should be done, and the *QIC* bits should be
checked for in mt_dposn to confirm this error).
o Attempting to do something when not at BOT that can only be
done at BOT, such as writing or reading a Kennedy tape drive
at a different speed than was previously used or switching
from the variable block size device to the fixed block size
device. (In IRIX 4.0, an attempt to use a different density
is allowed, but the drive continues to use the original
density.)
o Attempting to perform reads, writes, or ioctls other than
MTIOCGET on the {stat} device.
EIO A generic error occurred, such as a SCSI bus reset,
unrecoverable media error, and so on. Also occurs on close or
read/write if the media has been unloaded while the device is
open.
ENOMEM An attempt was made to read data with a count less than that at
which the block was written. This can only happen with drives
that support variable block sizes. It can also occur if the
kernel memory allocator is not able to allocate memory for the
driver structures, or the request exceeds maxdmasize for the
system.
ENOSPC Occurs on read or space commands that encounter end of tape or
end of data, on writes that are attempted at end of tape, and
also on some other commands that encounter EOT or EOD.
EROFS A write or write file-mark was attempted to a write-protected
tape.
ENODEV An open was attempted on a device with an invalid SCSI
controller or SCSI ID specified (that is, a mknod with the
wrong arguments was used to create the device special file) or
an attempt to open a tape in variable blocksize mode when the
device doesn't support it. Also occurs when the SCSI inquiry
command fails or returns indicating that the device is not a
tape device (media not removable, or not a sequential access
device).
NOTES
High density tape cartridges such as the DC6150 (originally called 600
XTD) written on a system equipped with QIC 150 tape drives can NOT be
read on older systems. Even if a low density tape (such as DC 600A) is
used, it is still written at a higher density (QIC 120) than older tape
drives can read. Tapes written on the older systems can still be read on
the new tape drives, however. Systems with QIC 150 cartridge tape drives
such as the Personal IRIS are able to read QIC24 tapes (310 oersted) such
as the DC 300XL, but are not able to write them.
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All tape devices other than the QIC (quarter-inch) tape drives have
/dev/tape linked to the {ns} device for performance, since there is no
compatibility issue, and byte swapping is done in software. Most newer
drives support variable block size devices, and the /dev/tape link uses
those by default; when multiple densities are supported, as with 9-track,
the link is to the highest capacity device. For compatibility with
earlier IRIX releases, the 8mm device is linked to the fixed block
device. See the (unfortunately somewhat confusing) script /dev/MAKEDEV
for details; in particular, look at the tapelinks target.
Each time the tape drive is closed and the drive has reported recovered
error, the driver reports to the console and (as normally configured) to
/var/adm/SYSLOG the number of recovered errors, if any. A small number
is not indicative of problems, but a large number (somewhere above about
2-5% errors as a percentage of I/Os, depending on media age and quality)
probably indicates that the media is approaching the end of its lifetime,
that the drive read/write heads are dirty, or that the heads need to be
realigned. A typical recovered error message might look like:
NOTICE: tps0d7 had 8 successfully retried commands (1% of r/w)
The first number is the controller number, the second is the SCSI ID on
that controller.
It is important to realize that these are recovered errors (at the drive
level) and therefore do not result in errors being reported to the
program doing the tape I/O.
It should be noted that the reported percentage of retried errors for
some devices, most notably EXABYTE, may be shown to be orders of
magnitude larger than the actual number of I/Os. This is not necessarily
indicative of a serious problem when one realizes how this value is
derived. The EXABYTE 8505, for example, when returning the number of
retried I/Os will report the number of retried 1Kbyte blocks, and hence
an alarmingly large reported percentage of retried errors.
With more recent versions of microcode, the Ampex DIS/DST series of
drives support variable length blocks. These should be detected as such
and the appropriate device names created. It is important to note that
even though variable blocks are supported, blocks smaller than 1,199,840
bytes will reduce cartridge capacity and throughput.
Nine track tape users wishing to read large blocks (i.e. "gapless") tapes
should obtain their drive from the M4 Data Corporation in Florida. They
should request the "SGI Long Block" feature to insure that the proper
microcode is installed in the 9914 drive. These drives will identify
themselves as "SGI" for the vendor and "GOLD SEAL" for the model. The
default master.d/scsi supplied by SGI includes a definition for this
drive. It is also important to check that maxdmasize is set correctly
for the system.
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/dev/rmt/tps*
/dev/rmt/*/lun*/c*p*
/dev/mt exists as a symlink to /dev/rmt; the use of the /dev/mt
pathname is deprecated and is supported only for
compatibility
/dev/tape, /dev/nrtape, /dev/tapens, /dev/nrtapens
convenience links to the "preferred" device in /dev/rmt
(highest SCSI ID on lowest numbered SCSI bus, for tps
devices only)
/var/sysgen/master.d/scsi
contains a configuration table indicating what devices
support what features and what string should be matched
against the string returned by the SCSI inquiry command
and the hinv(1M) command; this was formerly in
master.d/tpsc
/dev/MAKEDEV a makefile (normally invoked by the superuser in the /dev
directory only) that creates devices that match the
installed tape drives if invoked as cd /dev; ./MAKEDEV
tape
SEE ALSOMAKEDEV(1M), bru(1), cpio(1), hinv(1M), mt(1), tar(1), ioctl(2),
rmtops(3), datframe(4), mtio(7).
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