How can non-NetBackup applications and utilities read and write tapes when NetBackup requires that it has sole access to the tape drives?

Description

How can non-NetBackup applications and utilities read and write tapes when NetBackup requires that it has sole access to the tape drives?

NetBackup customers do sometimes need to read and write tapes with standard utilities like TAR and CPIO. Some applications also require direct tape access. For example, a vendor supplies a fix-tape in CPIO format, an application needs to dump a configuration set directly to tape, or a set of files are destined for a non-NetBackup site.

When NetBackup is installed, it comes with Media Manager. This is configured to manage the tape library, mounting and dismounting of tapes and drive access control. By default, if any other utility or application tries to access any of these resources outside of Media Manager control, problems occur; drives will be marked as DOWN, backups will fail, mounts or dismounts may fail as well as the intended user operation failing.

One method which is often used to resolve this conflict is to DOWN the drive manually, either from the command line with the vmoprcmd command or from the Device Monitor GUI. While this addresses the conflict of interest in the drive between Media Manger and the utility, it is unattractive for a number of reasons. Firstly, the user must remember to UP the drive when they have finished. If the user doesn't UP the drive, NetBackup will not use that drive. Secondly, the user is still left with the problem of how to get the tape mounted and dismounted. Finally, the user must be sure not to select the wrong tape, otherwise the user could over-write a NetBackup tape.

A more secure and reliable method is to use Media Manager for the entire process. The essence is to use the tpreq and tpunmount commands to mount and dismount tapes and get sole access to a drive while that tape is mounted. By using these commands, the user informs Media Manager that the user wants to access a tape directly. Media Manager will mount the requested tape in a drive of its choice, then create a symlink (symbolic link) to the actual tape device from a file specified by the user.

Further, by grouping all the tapes for use with a utility or application into a media pool, the chance of the wrong tape being used is further reduced. Consider the following example.

Example:

The administrator has been sent a DLT tape from a supplier which is in CPIO format. The tape has been inserted into the library and added to the CPIO pool. It has bar code A00001. To read the tape, the commands would be:

• Set the path to include the Media Manager commands.
  • PATH=$PATH:/usr/openv/volmgr/bin; export PATH
• Mount the first tape. Link the actual tape drive used to a temporary file called mytape.
  • Syntax: /usr/openv/volmgr/bin/tpreq -m media_id -d density -p poolname -f filename
  • Command: /usr/openv/volmgr/bin/tpreq -m A00001 -d dlt -p CPIO -f /tmp/mytape
• The tape is now mounted. You can reference /tmp/mytape as the tape device. It is linked to the non-rewind device, so its always best to force a rewind first and at the end.
  • mt -f /tmp/mytape rewind
• Now read the tape.
  • cd /where_you_want_to_read_tape_to
  • cpio -idvum < /tmp/mytape
• Tape was read. Now rewind and then tell Media Manager you've finished with it and ask for it to be unmounted.
  • mt -f /tmp/mytape rewind
  • tpunmount /tmp/mytape