IBM SG24-5131-00 manual How to do a split-mirror backup

8.7.1.1 How to do a split-mirror backup

This same procedure can be used with just one mirrored copy of a logical volume. If you remove a mirrored copy of a logical volume (and file system), and then create a new logical volume (and file system) using the allocation map from that mirrored copy, your new logical volume and file system will contain the same data as was in the original logical volume.

Now, you can mount this new file system (read-only is recommended), back it up, and you are really backing up a mirrored copy of the data in the original file system, as it was when we removed the mirror copy. Since this file system, created from the mirror copy, is mounted read-only, no inconsistency in the file system from the point at which you removed the mirror originally is created during the backup. After that, you can delete the new file system to release the physical partitions back to the free pool. Finally, you can add and synchronize a mirror back onto the original file system, and you are back to a mirrored mode of operation, with fully updated data.

The splitlvcopy command of AIX does much of the work required to implement this solution.

We can summarize the steps to do a split-mirror backup of a file system as follows:

1.Use the lsvg -l VGNAME command to take note of the logical volumet name that contains the file system you want to back up.

2.Stop any application using the file system and unmount the file system.

3.Use the splitlvcopy command to break off one mirror of the logical volume, and create a new logical volume with its contents. For example, if the existing logical volume is named fslv, the command would be splitlvcopy -y newlv fslv.

4.It is important to note that there is now one less mirror copy available to the user in fslv.

5.Remount the file system and restart the application that was using it.

6.You can see that the application and data are offline for only a very short time.

7.Create a file system on your new logical volume and mount it read-only. This is to ensure that no update activity will occur in the new logical volume, and the consistency of the file system is guaranteed.

8.Perform the backup on the new file system by any means desired, such as backup, tar, cpio, and pax.

Cluster Management and Administration 177