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|Special types of data migrations|
Network-based tools such as FalconStor Software's IPStor and DataCore Software's SANsymphony offer a vendor-neutral approach from an operating system and storage perspective. Yet these approaches sometimes make administrators uneasy because of the time required to set up these roducts.
Before a network-based migration commences, an administrator needs to set up zones, allocate LUNs on the new arrays and reboot servers so they can discover the new volumes on the new array. The amount of risk that something will go wrong correlates to how large the networked storage environment is and how well it's maintained and documented. Poorly maintained and documented storage area networks (SANs) may require weeks--if not months--to identify, schedule and verify each server's access to volumes on existing arrays, and also verify their access to volumes on the new arrays after they have been allocated. Migrating data from one database format to another presents a set of additional problems (see "Special types of data migrations").
Host-based replication technologies exist for nearly every major operating system platform, including mainframe, Novell, Windows and most flavors of Unix. The free utilities that ship with the operating systems should only be used with offline applications or files. Look for a third-party solution if you need to maintain application availability while moving data to a new storage location. Products differ in the number of steps required to perform the data migration and how they manage the process.
There are a number of good reasons to use host-based technologies for data migrations such as:
- Lack of money to purchase replication software
- Inexperience with array- and network-based solutions
- Comfort level with existing migration techniques
- Integration with existing databases or a mix of different vendor's storage arrays
- Migrates from anything (internal or external disk) to anything
- Inexpensive if used with existing OS utilities
- Can change volume characteristics during migration
- Requires root-level access to each server
- May need to install software in addition to migration software
- Need to uninstall software following the migration
Tools such as Veritas' StorageCentral and Storage Reporter track data usage and profile storage resources--information essential for a successful data migration. Once the migration begins, Veritas' Storage Foundation analyzes the amount of disk space that will be saved and shows a progress bar as the data is migrated.
Look for products that monitor network traffic during data migrations, and in the event of a network slowdown, store all source changes and transmit them when possible. They should also perform resyncing operations to get the target data back in sync with the source data. And ensure the tools have a central management console from which to manage the migration.
This was first published in May 2004