The UNIX volume manager method for migrating data is very similar
to the method that is used by AIX systems. It involves the use of commands
or a combination of commands that copy and move the data.
The following methods are available for the UNIX volume manager. The method
you choose depends on your operating environment.
- The cplv method
- Use the cplv command to make entire copies of logical volumes.
You can issue the cplv command without disrupting access to data that
is contained within the logical volume that it is copying. However, there
is one drawback to using this command. Active logical volumes might not be
copied when you use this command. You must ensure that your logical volumes
are closed before you run this command.
To ensure consistency and limit
the problems that are associated with this command, proceed with the following
process:
- Close your logical volumes either by unmounting the file system where
they are built on, or by shutting down any database that has an open raw logical
volume.
- Run the cplv command.
- Update the system configuration file, /etc/filesystems, to include
the relevant configuration data on the new logical volume and file system.
- Issue the fsck command to run the file system integrity checker
to ensure data consistency within the new logical volumes.
- The migratepv method
- This is an ideal method for moving data without disrupting users. Use
the migratepv command to create a mirror of each logical volume that
is contained within the physical volume. Issuing this command also synchronizes
both copies. The benefit of this command is that you can run it on an active
system.
You might notice some performance degradation due to the automatic
nature of the creation and the synchronization of the copy. This process writes
each physical partition and locks it from access by any other process. This
can slow down access to the data, but it ensures data integrity.
- The mklvcopy, splitlvcopy method
- This method is ideal for creating a copy of logical volumes. Use the mklvcopy command
to ensure data integrity by creating a mirror copy of the data and synchronizing
it automatically. Do not run the splitlvcopy command or the cplv command
on an active logical volume. If processes are updating the data while the
split is taking place, the consistency of the data on both copies cannot be
guaranteed. After you run the splitlvcopy command, update the system configuration
files. Include the relevant configuration data regarding the new logical volume
and file system. Then issue the fsck to run the file system integrity
checker to ensure data consistency within the new logical volume.
- The mklvcopy, rmlvcopy method
- This method is ideal for migrating active logical volumes when a slight
performance loss is acceptable. This method creates and removes mirrors automatically,
ensuring data integrity.