Moving data from your private cloud environment to IBM Power Virtual Server

Migrating volume group data by using the savevg command

A volume group is a collection of physical volumes of various sizes and types. When a physical volume is assigned to a volume group, the physical blocks of storage media are organized into physical partitions. You can specify the size of the physical partition when you create the volume group. You can use built-in AIX savevg and restvg commands to back up and restore non-root volume groups. The savevg and restvg commands simplify the creation of new volume groups and file systems on the new VM.

The savevg command finds and backs up all files that belong to a specified volume group. The volume group must be varied-on, and the file systems must be mounted. The savevg command uses the data file that the mkvgdata command creates.

Use the following command to find and back up all files in a specific volume group.

# savevg –f <destination path> -i <non root vg files to be backed up>

For example,

# savevg –f /home/admin01/datavg_bkup –i  datavg

Backing up multiple volume groups by using the mkvgdata and restvg commands

Small systems might require only one data volume group to contain all the physical volumes. For a non-root user you might want to create separate volume groups, for security reasons, because each volume group can have its own security permissions. If a volume group stops working, other volume groups remain active. Hence, separate volume groups are easier to maintain.

Run the following commands to back up multiple volume groups:

# lsvg -o | xargs -i mkvgdata {}
# tar -cvf /backup/vgdata.tar /tmp/vgdata

To generate an output file that contains information about the volume group, run the mkvgdata command for each online volume group to generate the output file. This output file is located in the /tmp/vgdata directory. You can compress and store this output file in the /backup file system directory as shown in the following example. This output file contains information about all volume groups, logical volumes, and file systems that can be used as a single image. This image can be transferred or stored within an mksysb backup image if the /backup directory is on the root volume group.

Run the following command to re-create the volume groups, logical volumes, and file systems:

# tar -xvf /backup/vgdata.tar

Now edit the /tmp/vgdata/{volume group name}/{volume group name}.data file and look for the line with VG_SOURCE_DISK_LIST=. Change the line to have hdisks, vpaths, or hdiskpowers based on your requirement.

For example,

# restvg -r -d /tmp/vgdata/{volume group name}/{volume group name}.data

Migrating raw partitions by using the dd command

The output file of the savevg command can be restored by using the restvg command. The size of a savevg backup file is small in comparison to the size of the physical volumes in the volume group. If the environments have several TBs of data, the prescribed method of moving volume group data by using the savevg command might present a disadvantage while considering transference and restoration procedures.

You can use the savevg command to back up volume groups. All logical volume information, Journaled File System (JFS), and JFS2 mounted file systems are archived. However, you cannot use the savevg command to back up raw logical volumes.

Use the following methods to back up and restore the contents of a file system:

1. Unmount the file system.
2. Save the raw logical volume content into a file by running the following command:

  # dd if=/dev/lvname of=/file/system/lvname.dd

This command creates a copy of the logical volume named lvname to a file named lvname.dd in the file system /file/system. Make sure that the specified directory where the output file will be stored (/file/system in the example) has enough available disk space to hold a full copy of the logical volume. For example, if the logical volume size is 100 GB, you need 100 GB file system space for the logical volume copy.

On the destination server, re-create the logical volume and the file system. If you are using an unmounted file system, run the following command to restore the backup copy:

# dd if=/file/system/lvname.dd of=/dev/lvname

After you run the dd command to mount the file system, you can access the contents of the original file system.