2 Replies Latest reply: Jul 20, 2017 3:04 AM by Wasfi Bounni RSS

How many journaled lun we need at each site?

Wasfi Bounni



Is it one journaled lun per SF-Core catering for all suspended state writes for all luns or we need a separate journaled lun for each production lun managed by a core device?




  • Re: How many journaled lun we need at each site?
    Tom Tasker

    Hi Wasfi,


    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.