In the storage consolidation realm, data migration -- the process of moving data from one storage location to another -- is crucial to storage preparation and ongoing management. For example, a new consolidated storage platform must be brought online and then receive data that is migrated to it from other storage systems before those older systems are decommissioned. For large consolidation initiatives, this might involve migrating data from multiple arrays or dozens (even hundreds) of file servers. After the initial migration, data still must be migrated to various tiers within the consolidated platform or periodically moved off to lower tier storage systems, such as disk-to-disk, virtual tape libraries (VTL) or tape.
But data migration for storage consolidation can be a difficult process. Knowing exactly what
Does the data migration tool support heterogeneity? Data migration products must operate across every platform involved in the storage consolidation initiative, including the new consolidated storage system, the existing systems being decommissioned or redeployed and any other storage systems that will receive offloaded data into the future. Some data migration products favor specific storage platforms, such as the SRDF family from EMC. Others favor specific application types, such as transactional database movement in Transactional Data Management (TDM), from GoldenGate Software Inc. Still others favor SAN or LAN (e.g. iSCSI or NAS) environments. Select the proper tool for your particular environment and data movement goals.
Migration criteria. You'll want a data migration plan. For example, some storage consolidation plans may implement data migration in phases from certain systems or initially moving data of a given age, type, access frequency or metadata content. Some migration software may copy data from the source(s) to the consolidated destination, but mirror writes to both locations to maintain synchronization until a final "cutover" occurs. Other migration software simply moves data between locations and deletes data from the source. As part of your plan, you'll want to weigh the impact of data migration on backups, disaster recovery, business continuance, regulatory compliance and legal discovery.
Retention and deletion capabilities. Once a storage infrastructure is consolidated, efficient consolidation must be maintained over time. One way to do this is to periodically move older or unnecessary data off the consolidated platform to a local or even remote storage system, such as a VTL. Another tactic is to implement data retention and deletion features, ensuring that critical data is preserved, while old data is eradicated within the compliance policies of your organization. If the data migration software itself doesn't provide such features, it should interface with other policy managers in the storage environment.
Software licensing costs. Data migration is performed as a series of steps implemented over time. These steps take place during the storage consolidation process and will continue afterward as data ages out of the consolidated platform. This means migration software must be maintained and updated, which can carry some hefty annual licensing costs. When comparing migration software, be sure to weigh the total cost of ownership (TCO) for each product, rather than just the upfront purchase cost.
Logging and reporting features. Data migration software should produce comprehensive reporting that completely documents the data that was moved. Consider the level of strategic reporting needed for management and tactical reporting needed for storage administration. Also look for any advanced storage resource management (SRM) features, like capacity planning or low-storage alerts.
Bandwidth-throttling capabilities. Data migration causes additional storage traffic within the SAN or LAN and within the storage platforms themselves. This additional traffic will often interfere with regular user and storage traffic, and can sometimes impair service levels. Understand how the migration will impact storage performance and consider a tool that will throttle the data migration process -- slowing migration during periods of heavy storage or network utilization. Veritas Volume Replicator from is just one example of data movement software that supports data movement throttling.
The level of disruption involved in data movement. Beyond bandwidth contention, data migration may also cause other disruptions for applications. For example, some databases may need to be quiesced while the migration takes place. In other cases, applications may need to be reconfigured to recognize and accommodate new storage locations. Storage virtualization is one means of minimizing disruptions. Virtualization creates a layer of abstraction that decouples applications from physical storage locations. An increasing number of migration tools, such as Rainfinity from EMC, promise nondisruptive data migration in virtualized environments.
Specifications are provided for the following data migration products:
This was first published in February 2008