UNIX Configuration Guide:
HP-UX Systems (HP9000 Series 700 only)

Configuration Switch Settings

Autoloader Switch Settings

HP-UX Device Files: Major and Minor Numbers

Minor Number Device File Parameters

Series 700 Major Number 121: Minor Number Format

Major Number 205: Minor Number Format

Device Filenames (pre-HP-UX 10.0): Major Numbers 54, 121

Device Filenames for HP-UX 10.0: Major Number 205

Options

Driver-specific options
for stape (Series 700 Major Number 205 only)

Device Special File Name--Example

Glossary

Configuration Switch Settings

The configuration switches for an HP SureStore DAT drive installed on an HP workstation (HP 9000/Series 700) should use the tape drive's default settings:

Changing switch 3 to ON will disable the Media Recognition System, but this is not recommended.

The tape drive can be configured to operate in immediate mode and with infinite flush by setting switches 6 and 8 to OFF. This improves the drive's performance by reducing the time it takes to write filemarks and data because all commands will be treated as immediate. The drawback is that if power fails during a write operation, any data in the buffer will be lost.

Connectivity with Operating Systems

The table below shows the earliest version of HP-UX to which the drives will connect:

If the DDS unit is correctly installed, the operating system kernel should already have the SCSI tape drivers configured. If you have any doubts, use the System Administration Manager (SAM) to check the kernel configuration.

HP SureStore DAT24x6 and DAT40x6:
Autoloader Option Switch Settings

HP SureStore DAT external autoloaders have an additional selector switch on the rear panel. This switch sets different configurations for the autoloader mechanism and are read by the firmware at power-on. For a DEC system, this switch should be set to 7 (the default value), which sets the internal switches as follows:

Note: Set the value with the autoloader switched off.

The HP SureStore DAT24 internal autoloaders also have an option selector on the rear panel. These are four on-off switches that allow you to set the value, as above. Instructions for setting these switches are provided in the Installation Guide. You should not need to change them after installation.

For a more detailed explanation, please see Autoloader Option Switches.

HP-UX Device Files: Major and Minor Numbers

Device files tell your host computer which system hardware path to use when communicating with a specific device and what type of device it is. The device files for HP SureStore DAT drives are located in the directory /dev/rmt.

An HP-UX device file is made up of a Major Number and a Minor Number. Major Number recommendations for Series 700 workstations are as follows:

• 121 is recommended as the preferred Major Number for HP-UX 9.x (54 will function satisfactorily from HP-UX 9.01 upwards but is not recommended.)
• 205 is the recommended Major Number for HP-UX 10.x

Each Major Number requires a different Minor Number format as described below. To check the Major and Minor Numbers on your workstation, use the lsdev command and look for the entry for SCSI tape driver.

On a Series 700, use the following commands to create device files:

• 'mknod' if you are using HP-UX 9.x or below
• 'mksf' if you are using HP-UX 10.x

Refer to your system's online man pages for further information about these commands.

Minor Number Device File Parameters

An HP-UX device file can be configured using the following parameters:

• Rewind and No Rewind Modes
• Berkeley and AT&T Modes
• Data Compression
• Buffered and Unbuffered Modes
• Variable and Fixed Block Modes
• Partition 0 and Partition 1
• Tape Format

Rewind and No Rewind Modes

Normally the drive repositions the tape to BOT (Beginning of Tape) when the device file is closed. This is set by device file Minor Numbers using the "rewind on close" option. To prevent this repositioning to BOT, use device file Minor Numbers with the "no rewind on close" option. The no-rewind option is useful when creating and reading multiple-file tapes.

Berkeley and AT&T Modes

Berkeley and AT&T functional modes differ in "read only" close functionality:

• In Berkeley mode the tape position will remain unchanged by a device close operation.
• In AT&T mode, a device close operation will cause the tape to be repositioned just after next tape filemark (the start of the next file).

In most cases, Berkeley mode should be used. It should always be used with mt.

Data Compression

Most HP SureStore DAT drives can read and write data using multiple data formats. Typically, different formats use different data densities. The following table shows the specific meaning of data densities with respect to DDS tapes.

Buffered and Unbuffered Modes

Write buffering (or immediate reporting) allows tape drives to indicate write completion as soon as data is received.This allows a tape device to achieve streaming (continuous media motion).

Device file Minor Numbers that set “buffering” cause write buffering (and hence streaming) to be enabled. Device file Minor Numbers that set “no buffering” cause write operations to be unbuffered (write completion is not indicated until the data has been written to tape).

Unbuffered mode is likely to reduce I/O performance and media capacity and cause the tape to make more passes over the tape head. This in turn reduces tape life. For this reason, the “buffering” option should normally be used.

Unbuffered mode is only available through device Major Number 205.

Variable and Fixed Block Modes

Data is written to tape in blocks. Device file Minor Numbers that set "variable" blocks cause data-block sizes to be determined by write system calls (each write system call causes one data block to be written to the tape). Normally, variable-length blocks are used.

Device file Minor Numbers that set fixed blocks cause data blocks of a consistent size to be written. The specific block size is determined by the tape device and the driver. In fixed-block mode, write system calls to a device file must be a specified number of bytes in length. Fixed-block mode can increase or decrease I/O performance and tape capacity (depending on the tape device and the specific fixed-block size).

Fixed-block size is only available through Major Number 205.

Partition 0 and Partition 1

Tapes usually contain a single partition (partition 0). HP DDS tape devices support the division of a tape into two partitions (two separate logical volumes, partition 1 and partition 0). Media can be partitioned by using the mediainit command with "-p" option. Partition 1 is nearest to BOT (Beginning of Tape); partition 0 is nearest to EOT (End of Tape).

If the last tape access was to Partition 0, the tape is not usually repositioned on an "open". However, device file Minor Numbers that set "partition 1" cause the tape to reposition to the beginning of partition 1 on an "open" when the tape contains multiple partitions and the last tape access was to Partition 0. If the last tape access was to partition 1, the tape is not repositioned on an "open" operation.

Tape partitioning and access to partition 1 require the use of Major Number 54.

Tape Format

The HP-UX 10.0 device file naming convention is a generalized scheme that permits flexibility in specifying the format of data written to tape for several different tape technologies.

For DDS drives, however, the format in which data is written to the tape is restricted and determined by the combination of device type and DDS cartridge type, rather than by the format specified in the device filename. Hence a drive will write to and read from a tape in a format compatible with the tape; for example, a DDS-2 cartridge in a DDS-3 drive will be recorded and read as a DDS-2 cartridge.

Series 700 Major Number 121:
Minor Number Format

An HP series 700 workstation running HP-UX 9.x should use Major Number 121 for which the Minor Number format is:

   0xBBBTLD

Where the parameters are as follows:

Example:

  % mknod /dev/rmt/3hcn c 121 0x20130F

This command line creates a device file the following options:

• Major Number 121, with data compression for DDS-DC format drives
• Connection onto the core SCSI bus
• SCSI ID 3
• LUN 0, partition 0
• Berkeley mode, no rewind on close option, compressed

Major Number 205: Minor Number Format

For HP-UX 10.x, use mksf (make special file) to create the device files for the tape drive. The mknod command is not recommended because it selects configuration options by directly setting bits in the Minor Number. With HPUX 10.0 and above, there are more configuration options than will fit in the device file’s Minor Number, so this direct set method is no longer possible. Use SAM to create device files using the Tape Device section of the Peripherals function.

To accommodate the additional configuration options available in HPUX10.x, the Minor Number contains a base set of options, while extended options are stored in a table of configuration properties. The Minor Number contains an index to this property table. The index is maintained by the tape driver and is not directly visible to the user.

The mksf command sets the Minor Number and modifies the property table as necessary. If the device configuration requirements are limited to the base set of options, the default property table should be correct. The base set of options is as follows: 

• Hardware address (card instance, target and logical unit number)
• Density (from the set of pre-defined options listed in mksf)
• Compression (using the default compression algorithm)
• Rewind or no rewind
• Berkeley or AT&T mode

See Device Configuration Parameters for more details of these.

All other configuration options are extended options that result in use of the property table.

You must put tape device files using extended configuration options in the /dev/rmt directory. This is necessary for proper maintenance of the property table.

Note: Use the rmsf command to clean up the unused device files, otherwise the property table may overflow and cause the mksf command to fail.

For conventions in naming device files, see Device Filenames: HP-UX 10.0

Device Filenames (pre-HP-UX 10.0):
Major Numbers 54, 121

Ideally, device filenames correspond to a device’s instance and its properties, as shown below. However, some common tape backup applications have built-in default device names, and you may need to ignore the standard naming convention for device filenames in this case. The standard convention is:

Where:

Device Filenames for HP-UX 10.0:
Major Number 205

The naming conventions defined in this section indicate the options used with each device. You can, however, create device files with names of your own choice.

For each tape device present, eight device files are automatically created for regular use when the system is initialized. (A ninth file can be created especially for use by system diagnostics.)

• Four of these device files, corresponding to the four permutations of the "n" and "b" options, use one of the naming conventions described below. When the standard naming convention is used, these four files contain the density specification "BEST". When the alternative convention is used, these four files contain the density specification "f0".
• The other four files, again corresponding to the permutations of "n" and "b", use the pre-HP-UX 10.0 device file-naming convention. The names include an arbitrary number to distinguish this tape device from others in the system, followed by the letter "m". They are created automatically when the system is initialized.

Each of the files using the standard or alternative naming conventions is linked to the corresponding device file using the pre-HP-UX 10.0 naming convention. Thus, the device files that use the pre-HP-UX 10.0 naming convention typically provide the same functionality as the device files which contain the density specification "BEST" or "f0".

There are two naming conventions in HP-UX 10.0 for device special files:

• The standard (and preferred) convention is used on systems that support long filenames. We recommend this because it allows for all possible configuration options in the device name and is used by the mksf command. The name structure is as follows:

  /dev/rmt/c#t#d#[o] [z] [e] [p] [s[#]] [w]<format>[c[#]] [n] [b]

• An alternative convention is provided for systems limited to short filenames. These device filenames are less descriptive, but do guarantee unique device naming and can be used by the mksf command where required.

  /dev/rmt/c#t#d# [f#] [i#] [n] [b]

Options

The options in the naming conventions are common to all HP-UX 10.0 tape drivers. The c#t#d# notation in the device special filename derives from ioscan output and is described in the man pages for ioscan and intro. For options unique to stape go to Driver-specific options for stape.

The options in the naming structure are as follows:

Driver-specific options for stape
    (Series 700 Major Number 205 only)

The following options (available only through the property table) can be used in creating device special files for tape drives which access the stape driver:

Device Special File Name--Example

For a device at SCSI card instance 1, target 2 (SCSI ID 2), LUN 0, with exhaustive mode enabled (see Driver-specific options for stape ), fixed block size of 512 bytes, DDS-1 density with compression, AT&T-style with no rewind on close, the standard device file special name would be:

   /dev/rmt/c1t2d0es512DDS1Cn

For a system requiring short file names, the same device special file would be named:

   /dev/rmt/c1t2d3i#n

Where # is an index value selected by the tape driver.

Use the lssf command to determine which configuration options are actually used with any device file.