Summary
This article describes the procedure for mapping multiple RAW LVM source drives to a single target disk.
Symptoms
One of the features of BMR in Linux is that several source disks can be mapped to a single target disk, if the following conditions are true:
- The target disk has more space than the total size of all the source disks.
- The volumes on all the source disks are from the same volume group.
The figure below shows this feature. Source disk sda has a volume group configured. Source disks sdb and sdc share the same volume group but a different volume group than sda. So the total size of both sdb and sdc is less than the size of the target disk - sdb. The size of the disk sdb and sdc are shown as RAW, because these disks don't have any partitions, thereby leading to the limitation which is addressed in this article.
The source disk sdb does not have any partition. So, although the size of source disks sdb and sdc together is less than that of the total size of the target sdb, when the target disk finds that the source does not have any partition, the entire target disk (sdb), will be assigned to that source disk (sdb). Thus, you cannot choose source disk sdc to be mapped to target disk sdb. The figure below shows that while trying to map both source sdb and source sdc to target sdb, an error message is displayed showing that the Volume Group cannot be restored.
Resolution
The work around for this issue is to map both the source disks to None and then click Next. By doing so, the logical volume can be mapped:
Click Yes:
Now map the source disks sdb and sdc to the target disk sdb:
Click Next for the BMR process to proceed: