The requirement is one Journal LUN per SteelFusion Core. That Journal LUN metrics are;
(Taken from the SteelFusion Design Guide on the Riverbed Support site)
Regardless of the number of LUNs in the data center that are being projected by Core and protected by FusionSync, you only need one Journal LUN for each data center. The LUN only needs to keep track of the write operations, so no actual data blocks are stored on the Journal LUN. Because no storage is required, the size of the Journal LUN is quite modest compared to the size of the LUNs on the backend storage array. You can size the Journal LUN with this formula:
- 1 GB for metadata + 2 GB minimum for each LUN protected by FusionSync.
Therefore a SteelFusion deployment that has 25 LUNs needs a 51-GB Journal LUN.
The size of the Journal LUN is checked against the number of LUNs it is configured to support for FusionSync. If the size is too small, then an alert is raised and the FusionSync replication service does not start. The Journal LUN can be thin-provisioned and, if required, it can also be dynamically increased in size.