In Xsan 1.x you can have multiple volumes. Each will consist of a given number of Storage Groups that in turn consist of a given number of LUNs, as we’ve described in the past. If you have multiple volumes then they will all use the same Metadata Controllers. Each additional volume will also need its own dedicated Metadata LUN. Therefore, if you have 4 volumes, with 4 LUNs of data storage in each volume then you will have a total of 16 LUNs for data and another 4 for metadata to total out 20 LUNs. Essentially by splitting it up this way you are loosing 4 LUNs (up to 20TB in storage in some cases) because of your design. Why would you design it this way? Well, performance mainly – or for replication (eg – replicate data between volumes or to a VTL that is warehoused on a second volume). But in many cases you can use affinities, as described earlier to actually control traffic speeds to get around the need for multiple volumes.