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Backups using Linux Logical Volume Manager

We plan to run a couple of SuSE Linux servers under z/VM. We also plan to allocate 1-n VM-minidisks (1 GB each) to "data-volume groups" using LVM. Has anybody done backups of volume groups allocated on VM minidisk spread over several 3390-9s disks? Volume dumps are not very helpful.
Thanks for your question. Fortunately, one of my colleagues at Sistina is in an even better position to answer your question. Heinz Mauelshagen wrote the Linux Logical Volume Manager now found in the Linux 2.4 kernel. Heinz and his team have advanced the original design to provide a new, advanced LVM (called LVM 2.0) that will be found in both the upcoming Linux 2.6 kernel and in the latest Linux 2.4 trees. Heinz agreed to provide an answer to your question, so you have him to thank for this enlightening response.

Heinz's answer:

I assume the tool for IBM mainframe VM volume dumps that you are referring to is ddr. This tool will not solve your problem, because it would back up data owned by several guest operating systems (in this case Linux virtual images) that is allocated to a disk split into minidisks, rather than just the particular volume for a particular Linux virtual image.

If you really want to do block level dumps of the LVM physical volumes (similar to ddr on physical disks at the VM level), you can use the Linux dd command. You need to be very careful to insure that the LVM physical volumes(known as PVs) are not accessed during the backup to make sure that a consistent PV volume image is created. Unfortunately, this is likely to be unacceptable in a production environment!

A better approach for high-uptime production environments would be to back up the LVM metadata in /etc/lvmconf/* and use LVM snapshots for consistent online backups of the logical volumes rather than the physical ones. In essence, what we are saying is that if you are backing up your Linux virtual images on the mainframe, it is best to use the Linux tools -- including LVM -- to accomplish this, rather than trying to use the mainframe volume backup tools, which know nothing about the Linux virtual image logical and physical volumes.

This was last published in November 2005

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