Understand the 3 major approaches to data migration

Application-based, file-based, and block-based migration all have their own merits and use cases. Choosing the right solution starts with understanding their differences.

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Fundamentally versatile. Block migration migrates data as one unit at the infrastructure level. There are no file system or application support or compatibility concerns because the block-level migration process does not require processing any data that resides on a storage device. Any applications or any file systems—from VMware’s VMFS, to hyperconverged environments, to horizontally scaled software-defined storage—can be migrated without any data content processing necessary.

Data security. Block-level migration is the only genuinely secure approach to data migration because the migration tool does not interpret any application or file data during the entire migration. It is even possible to migrate an encrypted file system without having the key to the file system.

Raw storage support. In specialized applications that do not consume data from a file system or that use a proprietary file system, block-level migration can be the only way to accomplish an accurate and volume-consistent migration.

Data integrity. Block-level migrations are much more straightforward compared to other migration approaches. The block-level data is mostly copied sequentially, and the entire storage device is synchronized as one unit. As a result, the data integrity of a completed migration can be independently verified with much less effort.

True live migration. Migration tools that perform block-level migration can migrate truly live data. It does not matter how that data is used in production. Whether the data is contained in a database or a file archive, whether files are constantly opened and locked, or even if file permissions change, block-level migration is always performed in the same manner.

Limitations of block-level data migration

Technically sophisticated. Although conceptually straightforward, block-level migrations are technically sophisticated. Unlike other migration approaches, block-level migration often involves specialized knowledge and techniques instead of the readily available OS-provided APIs. These include knowledge of Fibre Channel and iSCSI protocols, low-level OS-specific kernel operations, etc.

Scarcity of tools. Due to the sophistication and specialized nature of a block-level migration, fewer block-level migration tools are available. There are even fewer purpose-built, block-level migration tools, as most block-level synchronization solutions available today are designed for data protection and disaster recovery purposes.

Application transformation. Block-level migration provides an excellent way to migrate any data. However, when the application is being transformed, and the data needs to be changed, application-specific tools may be necessary. For example, when migrating an Oracle Database instance from an AIX host to a Linux host, an application-level logical migration may be preferable due to the byte-order differences between the two operating system’s architectures.

Application, file, or block?

As the volume of data that needs to be stored continues to balloon, organizations across the globe are wrestling with not only where to keep their data but how to optimize their storage environments. As storage technologies continue to advance, and the cloud becomes viable for high-performance databases and applications, data migration and data mobility become significant considerations.

The conversations about data types, goals, and ways to control storage costs are now taking center stage. The first step in the journey starts with understanding the options and then aligning the strategy to the goal.  

Sammy Tam is the vice president of engineering for Cirrus Data Solutions. As a founding member of the R&D team at Cirrus Data, Sammy has been instrumental in developing block-level data migration technologies and software. Based in Syosset, NY, Sammy leads the worldwide engineering and development team. For more information, visit www.cirrusdata.com.

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