The st driver now supports persistent errors (see mtio(7I) and asynchronous tape operations (see mtio(7I), aioread(3AIO), and aiowrite(3AIO)).

If the driver is opened for reading in a different format than the tape is written in, the driver overrides the user-selected format. For example, if a 1/4" cartridge tape is written in QIC-24 format and opened for reading in QIC-150, the driver will detect a read failure on the first read and automatically switch to QIC-24 to read the data.

Note that if the low density format is used, no indication is given that the driver has overridden the user-selected format. Other formats issue a warning message to inform the user of an overridden format selection. Some devices automatically perform this function and do not require driver support (1/2" reel tape drive, for example).

Writing from the beginning of tape is performed in the user-specified format. The original tape format is used for appending onto previously written tapes.

The st tape driver has a built-in configuration table for all Sun supported tape drives. To support the addition of third party tape devices or to override a built-in configuration, device information can be supplied in st.conf as global properties that apply to each node, or as properties that are applicable to one node only. The st driver looks for the property called "tape-config-list." The value of this property is a list of triplets, where each triplet consists of three strings.

The formal syntax is:

tape-config-list = <triplet> [, <triplet> *];

where

<triplet> := <vid+pid>, <pretty print>, <data-property-name>

and

<data-property-name> = <version>, <type>, <bsize>, <options>, <number of densities>, <density> [, <density>*], <default-density>;

or

<data-property-name> = <version 2>, <type>, <bsize>, <options>, <number of densities>, <density> [, <density>*], <default-density>, <non-motion time-out>, <I/O time-out>, <rewind time-out>, <space time-out>, <load time-out>, <unload time-out>, <erase time-out>;

A semicolon (;) is used to terminate a prototype devinfo node specification. Individual elements listed within the specification should not be separated by a semicolon. (Refer to driver.conf(4) for more information.)

<vid+pid> is the string that is returned by the tape device on a SCSI inquiry command. This string may contain any character in the range 0x20-0x7e. Characters such as " " " (double quote) or " ' " (single quote), which are not permitted in property value strings, are represented by their octal equivalent (for example, \042 and \047). Trailing spaces may be truncated.

<pretty print> is used to report the device on the console. This string may have zero length, in which case the <vid+pid> will be used to report the device.

<data-property-name> is the name of the property which contains all the tape configuration values (such as <type>, <bsize>, etc.) corresponding for the tape drive for the specified <vid+pid>.

<version> is a version number and should be 1 or 2. In the future, higher version numbers may be used to allow for changes in the syntax of the <data-property-name> value list.

<type> is a type field. Valid types are defined in /usr/include/sys/mtio.h. For third party tape configuration, the following generic types are recommended:

<bsize> is the preferred block size of the tape device. The value should be 0 for variable block size devices.

<options> is a bit pattern representing the devices, as defined in /usr/include/sys/scsi/targets/stdef.h. Valid flags for tape configuration are:

ST_VARIABLE

The flag indicates the tape device supports variable length record sizes.

ST_QIC

The flag indicates a Quarter Inch Cartridge (QIC) tape device.

ST_REEL

The flag indicates a 1/2-inch reel tape device.

ST_BSF

If flag is set, the device supports backspace over EOF marks (bsf - see mt(1)).

ST_BSR

If flag is set, the tape device supports the backspace record operation (bsr - see mt(1)). If the device does not support bsr, the st driver emulates the action by rewinding the tape and using the forward space record (fsf) operation to forward the tape to the correct file. The driver then uses forward space record (fsr - see mt(1)) to forward the tape to the correct record.

ST_LONG_ERASE

The flag indicates the tape device needs a longer time than normal to erase.

ST_AUTODEN_OVERRIDE

The auto-density override flag. The device is capable of determining the tape density automatically without issuing a "mode-select"/"mode-sense command."

ST_NOBUF

The flag disables the device's ability to perform buffered writes. A buffered write occurs when the device acknowledges the completion of a write request after the data has been written to the device's buffer, but before all of the data has been written to the tape.

ST_KNOWS_EOD

If flag is set, the device can determine when EOD (End of Data) has been reached. When this flag is set, the st driver uses fast file skipping. Otherwise, file skipping happens one file at a time.

ST_UNLOADABLE

The flag indicates the device will not complain if the st driver is unloaded and loaded again (see modload(1M) and modunload(1M)). That is, the driver will return the correct inquiry string.

ST_SOFT_ERROR_REPORTING

The flag indicates the tape device will perform a "request sense" or "log sense" command when the device is closed. Currently, only Exabyte and DAT drives support this feature.

ST_LONG_TIMEOUTS

The flag indicates the tape device requires timeouts that are five times longer than usual for normal operation.

ST_BUFFERED_WRITES

This option is obsolete; if specified, it is ignored. Installations which previously used this feature should refer to the documentation on asynchronous I/O: aioread(3AIO) and aiowrite(3AIO).

ST_NO_RECSIZE_LIMIT (SPARC Only)

The flag applies to variable-length tape devices. If this flag is set, the record size is not limited to a 64 Kbyte record size. The record size is only limited by the smaller of either the record size supported by the device or the maximum DMA transfer size of the system. (Refer to Large Record Sizes and WARNINGS.)

ST_MODE_SEL_COMP

If the ST_MODE_SEL_COMP flag is set, the driver determines which of the two mode pages the device supports for selecting or deselecting compression. It first tries the Data Compression mode page (0x0F); if this fails, it tries the Device Configuration mode page (0x10). Some devices, however, may need a specific density code for selecting or deselecting compression. Please refer to the device specific SCSI manual. When the flag is set, compression will be enabled only if the "c" or "u" device is used. For any other device densities, compression will be disabled.

ST_NO_RESERVE_RELEASE

The ST_NO_RESERVE_RELEASE flag disables the use of reserve on open and release on close. If an attempt to use a ioctl of MTRESERVE or MTRELEASE on a drive with this flag set, it will return an error of ENOTTY (inappropriate ioctl for device).

ST_READ_IGNORE_ILI

The ST_READ_IGNORE_ILI flag is applicable only to variable block devices which support the SILI bit option. The ST_READ_IGNORE_ILI flag indicates that SILI (supress incorrect length indicator) bit will be set during reads. When this flag is set, short reads (requested read size is less than the record size on the tape) will be successful and the number of bytes transferred will be equal to the record size on the tape. The tape will be positioned at the start of the next record skipping over the extra data (the remaining data has been has been lost). Long reads (requested read size is more than the record size on the tape) will see a large performance gain when this flag is set, due to overhead reduction. When this flag is not set, short reads will return an error of ENOMEM.

ST_READ_IGNORE_EOFS

The ST_READ_IGNORE_EOFS flag is applicable only to 1/2" Reel Tape drives and when performing consecutive reads only. It should not be used for any other tape command. Usually End-of-recorded-media (EOM) is indicated by two EOF marks on 1/2" tape and application cannot read past EOM. When this flag is set, two EOF marks no longer indicate EOM allowing applications to read past two EOF marks. In this case it is the responsibility of the application to detect end-of-recorded-media (EOM). When this flag is set, tape operations (like MTEOM) which positions the tape at end-of-recorded-media will fail since detection of end-of-recorded-media (EOM) is to be handled by the application. This flag should be used when backup applications have embedded double filemarks between files.

ST_SHORT_FILEMARKS

The ST_SHORT_FILEMARKS flag is applicable only to EXABYTE 8mm tape drives which supports short filemarks. When this flag is set, short filemarks will be used for writing filemarks. Short filemarks could lead to tape incompatible with some otherwise compatible device. By default long filemarks will be used for writing filemarks.

ST_EJECT_TAPE_ON_CHANGER_FAILURE

If ST_EJECT_TAPE_ON_CHANGER_FAILURE flag is set, the tape will be ejected automatically if the tape cartridge is trapped in the medium due to positioning problems of the medium changer.

The following ASC/ASCQ keys are defined to the reasons for causing tape ejection if ST_EJECT_TAPE_ON_CHANGER_FAILURE option is set to 0x200000:

Sense ASC/ASCQ Description

Key

4 15/01 Mechanical Failure

4 44/00 Internal Target Failure

2 53/00 Media Load or Eject Failed

4 53/00 Media Load or Eject Failed

4 53/01 Unload Tape Failure

ST_RETRY_ON_RECOVERED_DEFERRED_ERROR

If ST_RETRY_ON_RECOVERED_DEFERRED_ERROR flag is set, the st driver will retry the last write if this cmd caused a check condition with error code 0x71 and sense code 0x01. Some tape drives, notably the IBM 3090, require this option.

<number of densities> is the number of densities specified. Each tape drive can support up to four densities. The value entered should therefore be between 1 and 4; if less than 4, the remaining densities will be assigned a value of 0x0.

<density> is a single-byte hexadecimal number. It can either be found in the device specification manual or be obtained from the device vendor.

<default-density> has a value between 0 and (<number of densities> - 1).

<non-motion time-out> Time in seconds that the drive should be able to perform any SCSI command that doesn't require tape to be moved. This includes mode sense, mode select, reserve, release, read block limits, and test unit ready.

<I/O time-out> Time in seconds to perform data transfer I/O to or from tape including worst case error recovery.

<rewind time-out> Time in seconds to rewind from anywhere on tape to BOT including worst case recovery forcing buffered write data to tape.

<space time-out> Time in seconds to space to any file, block or end of data on tape. Including worst case when any form of cataloging is invalid.

<load time-out> Time in seconds to load tape and be ready to transfer first block. This should include worst case recovery reading tape catalog or drive specific operations done at load.

<unload time-out> Time in seconds to unload tape. Should include worst case time to write to catalog, unthread, and tape cartridge unloading. Also should include worst case time for any drive specific operations that are preformed at unload. Should not include rewind time as the driver rewinds tape before issuing the unload.

<erase time-out> Time in seconds to preform a full (BOT to EOT) erase of longest medium with worst case error recovery.

Each device maintains I/O statistics both for the device and for each partition allocated on that device. For each device/partition, the driver accumulates reads, writes, bytes read, and bytes written. The driver also takes hi-resolution time stamps at queue entry and exit points, which facilitates monitoring the residence time and cumulative residence-length product for each queue.

Each device also has error statistics associated with it. These must include counters for hard errors, soft errors and transport errors. Other data may be implemented as required.

The following is an example of a global tape-config-list property:

tape-config-list =
		"Magic DAT", "Magic 4mm Helical Scan", "magic-data",
		"Major Appliance", "Major Appliance Tape", "major-tape";


magic-data    = 1,0x34,1024,0x1639,4,0,0x8c,0x8c,0x8c,3;
major-tape = 2,0x3c,0,0x18619,4,0x0,0x0,0x0,0x0,3,0,0,30,120,0,0,36000;

name="st" class="scsi"
          target=0 lun=0;
name="st" class="scsi"
          target=1 lun=0;
name="st" class="scsi"
          target=2 lun=0;
          .
          .
          .
name="st" class="scsi"
          target=6 lun=0;

The following is an example of a tape-config-list property applicable to target 2 only:

name="st" class="scsi"
        target=0 lun=0;
name="st" class="scsi"
        target=1 lun=0;
name="st" class="scsi"
        target=2 lun=0
        tape-config-list =
        "Magic   DAT", "Magic 4mm Helical Scan", "magic-data"
        magic-data = 1,0x34,1024,0x1639,4,0,0x8c,0x8c,0x8c,3;
name="st" class="scsi"
        target=3 lun=0;
          .
          .
          .
name="st" class="scsi"
        target=6 lun=0;

To support applications such as seismic programs that require large record sizes, the flag ST_NO_RECSIZE_LIMIT must be set in drive option in the configuration entry. A SCSI tape drive that needs to transfer large records should OR this flag with other flags in the 'options' field in st.conf. (Refer to Tape Configuration.) By default, this flag is set for the built-in config entries of Archive DAT and Exabyte drives.

If this flag is set, the st driver issues a SCSI-2 READ BLOCK LIMITS command to the device to determine the maximum record size allowed by it. If the command fails, st continues to use the maximum record sizes mentioned in the mtio(7I) man page.

If the command succeeds, st restricts the maximum transfer size of a variable-length device to the minimum of that record size and the maximum DMA size that the host adapter can handle. Fixed-length devices are bound by the maximum DMA size allocated by the machine. Note that tapes created with a large record size may not be readable by earlier releases or on other platforms.

(Refer to the WARNINGS section for more information.)

The Emulex drives have only a physical end of tape (PEOT); thus it is not possible to write past EOT. All other drives have a logical end of tape (LEOT) before PEOT to guarantee flushing the data onto the tape. The amount of storage between LEOT and PEOT varies from less than 1 Mbyte to about 20 Mbyte, depending on the tape drive.

If EOT is encountered while writing an Emulex, no error is reported but the number of bytes transferred is 0 and no further writing is allowed. On all other drives, the first write that encounters EOT will return a short count or 0. If a short count is returned, then the next write will return 0. After a zero count is returned, the next write returns a full count or short count. A following write returns 0 again. It is important that the number and size of trailer records be kept as small as possible to prevent data loss. Therefore, writing after EOT is not recommended.

Reading past EOT is transparent to the user. Reading is stopped only by reading EOF's. For 1/2" reel devices, it is possible to read off the end of the reel if one reads past the two file marks which mark the end of recorded media.

Write/read: not modulo <n> block size

Recovery by resets failed

Periodic head cleaning required

Soft error rate (<n>%) during writing/reading was too high

SCSI transport failed: reason 'xxxx': {retrying|giving up}

Tape not inserted in drive

Transport rejected

Retrying command

Giving up

No target struct for st%d

File mark detected

End-of-media detected

Exabyte soft error reporting failed. DAT soft error reporting failed

Log sense parameter code does not make sense

Restoring tape position at fileno=%x, blkno=%lx....

Failed to restore the last <file/block> position: 
In this state, tape will be loaded at BOT during next open

Device does not support compression

DAT soft error reset failed

Errors after pkt alloc (b_flags=0x%x, b_error=0x%x)

Incorrect length indicator set

Data property (%s) has no value
Data property (%s) incomplete
Version # for data property (%s) greater than 1

st_attach-RESUME: tape failure tape position will be lost

Write Data Buffering has been deprecated. Your applications should 
continue to work normally. However, they should be ported to use 
Asynchronous I/O.

Cannot detach: fileno=%x, blkno=%lx

Variable record length I/O
Fixed record length (%d byte blocks) I/O

Command will be retried
 un_ncmds: %d can't retry cmd