patch-2.4.2 linux/Documentation/s390/TAPE

• Lines: 126
• Date: Fri Feb 16 15:53:08 2001
• Orig file: v2.4.1/linux/Documentation/s390/TAPE
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.1/linux/Documentation/s390/TAPE linux/Documentation/s390/TAPE
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+Channel attached Tape device driver 
+
+-----------------------------WARNING-----------------------------------------
+This driver is considered to be EXPERIMENTAL. Do NOT use it in 
+production environments. Feel free to test it and report problems back to us. 
+-----------------------------------------------------------------------------
+
+The LINUX for zSeries tape device driver manages channel attached tape drives 
+which are compatible to IBM 3480 or IBM 3490 magnetic tape subsystems. This 
+includes various models of these devices (for example the 3490E). 
+
+
+Tape driver features 
+
+The device driver supports a maximum of 128 tape devices. 
+No official LINUX device major number is assigned to the zSeries tape device 
+driver. It allocates major numbers dynamically and reports them on system 
+startup. 
+Typically it will get major number 254 for both the character device front-end 
+and the block device front-end. 
+
+The tape device driver needs no kernel parameters. All supported devices 
+present are detected on driver initialization at system startup or module load.
+The devices detected are ordered by their subchannel numbers. The device with 
+the lowest subchannel number becomes device 0, the next one will be device 1 
+and so on. 
+
+
+Tape character device front-end 
+
+The usual way to read or write to the tape device is through the character 
+device front-end. The zSeries tape device driver provides two character devices
+for each physical device -- the first of these will rewind automatically when 
+it is closed, the second will not rewind automatically. 
+
+The character device nodes are named /dev/rtibm0 (rewinding) and /dev/ntibm0 
+(non-rewinding) for the first device, /dev/rtibm1 and /dev/ntibm1 for the 
+second, and so on. 
+
+The character device front-end can be used as any other LINUX tape device. You 
+can write to it and read from it using LINUX facilities such as GNU tar. The 
+tool mt can be used to perform control operations, such as rewinding the tape 
+or skipping a file. 
+
+Most LINUX tape software should work with either tape character device. 
+
+
+Tape block device front-end 
+
+The tape device may also be accessed as a block device in read-only mode. 
+This could be used for software installation in the same way as it is used with 
+other operation systems on the zSeries platform (and most LINUX 
+distributions are shipped on compact disk using ISO9660 filesystems). 
+
+One block device node is provided for each physical device. These are named 
+/dev/btibm0 for the first device, /dev/btibm1 for the second and so on. 
+You should only use the ISO9660 filesystem on LINUX for zSeries tapes because 
+the physical tape devices cannot perform fast seeks and the ISO9660 system is 
+optimized for this situation. 
+
+
+Tape block device example 
+
+In this example a tape with an ISO9660 filesystem is created using the first 
+tape device. ISO9660 filesystem support must be built into your system kernel
+for this. 
+The mt command is used to issue tape commands and the mkisofs command to 
+create an ISO9660 filesystem: 
+
+- create a LINUX directory (somedir) with the contents of the filesystem 
+     mkdir somedir
+     cp contents somedir 
+
+- insert a tape 
+
+- ensure the tape is at the beginning 
+     mt -f /dev/ntibm0 rewind 
+
+- set the blocksize of the character driver. The blocksizes 512, 1024
+  and 2048 bytes are supported by ISO9660. 1024 is the default, u
+  which will be used here. 
+     mt -f /dev/ntibm0 setblk 1024 
+
+- write the filesystem to the character device driver 
+     mkisofs -o /dev/ntibm0 somedir 
+
+- rewind the tape again 
+     mt -f /dev/ntibm0 rewind 
+
+- Now you can mount your new filesystem as a block device: 
+     mount -t iso9660 -o ro,block=1024 /dev/btibm0 /mnt 
+
+TODO List 
+
+- The backend code has to be enhanced to support error-recovery actions. 
+
+- The seeking algorithm of the block device has to be improved to speed 
+  things up 
+
+BUGS 
+
+There are lots of weaknesses still in the code. This is why it is EXPERIMENTAL.
+If an error occurs which cannot be handled by the code you will get a 
+sense-data dump.In that case please do the following: 
+
+1. set the tape driver debug level to maximum: 
+     echo 6 >/proc/s390dbf/tape/level 
+
+2. re-perform the actions which produced the bug. (Hopefully the bug will 
+   reappear.) 
+
+3. get a snapshot from the debug-feature: 
+     cat /proc/s390dbf/tape/hex_ascii >somefile 
+
+4. Now put the snapshot together with a detailed description of the situation 
+   that led to the bug: 
+ - Which tool did you use? 
+ - Which hardware do you have? 
+ - Was your tape unit online? 
+ - Is it a shared tape unit? 
+
+5. Send an email with your bug report to: 
+     mailto:Linux390@de.ibm.com 
+
+