Accusys ExaSAN A12S2-PS - Manual (Page 93)

4. How to Use
User Guide Page 4-42
4.1.2.8.5 Snapshot
A snapshot is initialized with a data sync task running in the background to duplicate
the data from a source to a target. The host I/O data is also replicated in the target.
The mirror snapshot is offered by the ExaSAN RAID controller.
Note
The source and target volume of the snapshot must be identical.
Before setting a snapshot, you need to set the slice in the array. The capacity of each
slice and the number of shots should be in accordance with the space you need.
Suppose that an array has the capacity of 30 TB, you may divide it into three slices of
10TB. You must set the LUN map for the first slice. Setting the LUN map for the other two
slices is not required.
In the figure above, a snapshot can be created by splitting the source and target after
the background sync is completed. The I/O mirroring is stopped, and the difference is
under tracking in a bitmap table to support fast re-sync.