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146 DS6000 Series: Concepts and Architecture
8.5.1 Operating system mirroring
Logical volume mirroring (LVM) and Veritas Volume Manager have little or no application
service disruption and the original copy will stay intact while the second copy is being made.
The disadvantages of this approach include:
Host cycles are utilized.
It is labor intensive to set up and test.
Application delays are possible due to dual writes occurring.
This method does not allow for point-in-time copy or easy backout once the first copy is
removed.
8.5.2 Basic commands
Basic commands such as cpio (in a UNIX environment) or copy (in a Windows environment)
are common and easy to use. The disadvantages of basic commands are:
Length of service disruption varies by commands used.
They are tedious to handle large amount of LUNs.
Command scripting is prone to human error.
Security file level access issues can arise, depending on which commands used.
8.5.3 Software packages
The user can have data migration, backup or restore packages, and database tools to
migrate data. An example of a data migration package is BRMS (Backup Recovery and
Media Services). Tivoli Storage Manager (TSM) can also be used in a backup and restore
fashion to achieve data migrations. DB2 utilities and tools such as unload, load and copy may
also be used to migrate data. Other third-party data migration, backup and restore, and
database packages are available. Contact the respective vendor for further assistance.
The advantages of using software packages are:
Small application impact when using data migration package.
Little disruption for non-database files.
Backup or restore cycles offloaded to another server.
Standard database utilities.
The disadvantages of using a software package are:
Cost of data migration package.
Bigger impact and or disruption with large databases due to lack of checkpoint-restart
abilities.
Possibly lengthy application outage to backup and or restore environment.
Application service interruption.
8.5.4 Remote copy technologies
Remote copy technologies include synchronous and asynchronous mirroring. They include
Metro Mirror, Global Mirror and Global Copy.