Billions of files moved, each one verified to be identical to the source file and this was just at one Healthcare customer. In addition all the meta-data, time stamps and permissions were also verified. At DTS we eat, live and breathe file system data migrations and can help minimize risk from typical migration challenges. File system migrations are notoriously complex and labor intensive projects made even worse by the scaling of modern NAS systems. Switching storage vendors adds another level of complexity due to the operational and configuration differences of retention and multi-protocol support.
Business Challenges include:
- Disruption of service
- File inconsistencies due to resynching
- Planning outage windows
- Meeting compliance requirements
- Script development and monitoring
- Resynching files during migration phases
- Maintaining original time stamps
- Maintaining ACLS and permissions
- Passing/managing of retention
- Mixed mode (multi-protocol support)
- Project management
In-band and out-of-band are the two primary file system migration methods. DTS provides both options to customers. Each method has its advantages and disadvantages which are covered below.
Out-of-Band / Phased Migration
Out-of-band is a phased file system migration process in which a base line copy of the files are made to the new target. Then one or more incremental copies are made to capture the activity, including new files, deleted files and modified files, since the completion of the base line copy. A final incremental copy is made just before the final cut-over. Then there is an outage window to take the legacy system off-line and replace it with the new system. The advantage of the Out-of-band or phased approach is that there is no access disruption until the final cutover and no latency is introduced to the data path. The disadvantages of this approach are: it is lots of extra work to insure file consistency by resynchronizing edits to files already copied, consume more storage on legacy system.
A virtualization layer is inserted in the data path between the users/ applications and the storage systems. The virtualization layer, in the case of DTS is a virtual file system, that proxies both the existing file system/source storage as well as the new target. The primary advantages of this approach are: 1) Simplicity – it is a lot less work 2) Users are assured that they are always working with the latest version of a file 3) Project duration is shorter 4) Cut-overs are a 5 minute task. The disadvantages to this approach are: 1) There is a five minute outage to insert the virtualization layer into the data path 2) The virtualization layer adds a few milliseconds of latency for processing.
Our Professional Services team is available to learn about your environment, priorities and concerns. We can then the help you decide which approach is best for your situation.