In the third part to this four-part series, Migration with DataCore SANsymphony – Part 3, we discussed migration type #2, which was about Asynchronous Migration.
Now in our final segment we’ll take a dive into our third and final type of migration, Pass-through Snapshot.
MIGRATION TYPE #3: PASS-THROUGH SNAPSHOT
Pass-through Snapshot refers to migrating the data between two physical storage arrays attached to the same DataCore engine using DataCore Snapshot. Pass-through is a feature that allows attaching an existing storage array with data present to the DataCore engine for the purposes of “passing-through” the original volume to the original application server(s). Once in this mode, features such as Snapshot are available to be used against the newly passed-through source volumes.
In this scenario, a primary volume from one array (i.e. Volume_SRC) is snapped to a secondary volume from another array (i.e. Volume_SRC_Snap).
The full snapshot operation copies all data from the primary over to secondary while the primary is being accessed by the application server(s). Additionally, once the full snap operation is completed, DataCore tracks the changes that occur on the primary volume. At a later time, a Snapshot Update command can be issued to the snapshot bringing the secondary volume up-to-date with the changes that occurred on the primary volume.
The method of performing a snapshot from one storage system to another is an effective way of migrating large amounts of data at a local site from one array to another with only one DataCore engine deployed while maintaining access to the original data.
CONCLUSION
DataCore SANsymphony provides very powerful data migration features which emerge from its ability to interoperate with common block storage devices. In this article, we covered the concept of migrating existing storage devices in a mode called Pass-Through. DataCore can also perform data migration in its native Pool Mode (where the backing storage devices remain under full control of SANsymphony). Pool Mode provides the following benefits:
- Allows non-disruptive storage hardware upgrades
- Clears and reclaims space occupied on the original drive(s)
- Allows decommissioning of active physical disks non-disruptively from pools and redistributes their contents among the remaining disks in the pool
- Maintains redundancy and performance during major maintenance operations, upgrades, and expansions
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