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123 lines
4.4 KiB
123 lines
4.4 KiB
20 years ago
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Channel attached Tape device driver
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-----------------------------WARNING-----------------------------------------
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This driver is considered to be EXPERIMENTAL. Do NOT use it in
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production environments. Feel free to test it and report problems back to us.
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-----------------------------------------------------------------------------
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The LINUX for zSeries tape device driver manages channel attached tape drives
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which are compatible to IBM 3480 or IBM 3490 magnetic tape subsystems. This
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includes various models of these devices (for example the 3490E).
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Tape driver features
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The device driver supports a maximum of 128 tape devices.
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No official LINUX device major number is assigned to the zSeries tape device
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driver. It allocates major numbers dynamically and reports them on system
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startup.
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Typically it will get major number 254 for both the character device front-end
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and the block device front-end.
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The tape device driver needs no kernel parameters. All supported devices
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present are detected on driver initialization at system startup or module load.
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The devices detected are ordered by their subchannel numbers. The device with
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the lowest subchannel number becomes device 0, the next one will be device 1
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and so on.
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Tape character device front-end
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The usual way to read or write to the tape device is through the character
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device front-end. The zSeries tape device driver provides two character devices
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for each physical device -- the first of these will rewind automatically when
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it is closed, the second will not rewind automatically.
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The character device nodes are named /dev/rtibm0 (rewinding) and /dev/ntibm0
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(non-rewinding) for the first device, /dev/rtibm1 and /dev/ntibm1 for the
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second, and so on.
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The character device front-end can be used as any other LINUX tape device. You
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can write to it and read from it using LINUX facilities such as GNU tar. The
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tool mt can be used to perform control operations, such as rewinding the tape
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or skipping a file.
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Most LINUX tape software should work with either tape character device.
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Tape block device front-end
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The tape device may also be accessed as a block device in read-only mode.
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This could be used for software installation in the same way as it is used with
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other operation systems on the zSeries platform (and most LINUX
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distributions are shipped on compact disk using ISO9660 filesystems).
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One block device node is provided for each physical device. These are named
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/dev/btibm0 for the first device, /dev/btibm1 for the second and so on.
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You should only use the ISO9660 filesystem on LINUX for zSeries tapes because
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the physical tape devices cannot perform fast seeks and the ISO9660 system is
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optimized for this situation.
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Tape block device example
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In this example a tape with an ISO9660 filesystem is created using the first
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tape device. ISO9660 filesystem support must be built into your system kernel
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for this.
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The mt command is used to issue tape commands and the mkisofs command to
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create an ISO9660 filesystem:
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- create a LINUX directory (somedir) with the contents of the filesystem
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mkdir somedir
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cp contents somedir
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- insert a tape
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- ensure the tape is at the beginning
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mt -f /dev/ntibm0 rewind
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- set the blocksize of the character driver. The blocksize 2048 bytes
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is commonly used on ISO9660 CD-Roms
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mt -f /dev/ntibm0 setblk 2048
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- write the filesystem to the character device driver
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mkisofs -o /dev/ntibm0 somedir
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- rewind the tape again
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mt -f /dev/ntibm0 rewind
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- Now you can mount your new filesystem as a block device:
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mount -t iso9660 -o ro,block=2048 /dev/btibm0 /mnt
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TODO List
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- Driver has to be stabilized still
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BUGS
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This driver is considered BETA, which means some weaknesses may still
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be in it.
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If an error occurs which cannot be handled by the code you will get a
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sense-data dump.In that case please do the following:
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1. set the tape driver debug level to maximum:
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echo 6 >/proc/s390dbf/tape/level
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2. re-perform the actions which produced the bug. (Hopefully the bug will
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reappear.)
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3. get a snapshot from the debug-feature:
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cat /proc/s390dbf/tape/hex_ascii >somefile
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4. Now put the snapshot together with a detailed description of the situation
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that led to the bug:
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- Which tool did you use?
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- Which hardware do you have?
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- Was your tape unit online?
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- Is it a shared tape unit?
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5. Send an email with your bug report to:
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mailto:Linux390@de.ibm.com
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