IBM XIV Storage System Copy Services and Migration

8.11 Future configuration tasksThe section documents additional tasks that may be necessary after installation andmigration is complete.8.11.1 Adding additional capacity to the XIVIf and when additional capacity is added to a partially populated XIV, take the following steps:1. IBM adds the additional modules as a hardware upgrade (known as an MES). Theadditional capacity appears as free space once the IBM Service Representative hascompleted the process to equip these modules.Note: If the XIV has the Capacity on Demand (CoD) feature, then no hardware changeor license key is necessary to use available capacity that has not yet been purchased.The customer simply starts using additional capacity as required until all availableusable space is allocated. The billing process to purchase this capacity occursafterwards.2. From the Pools section of the XIV GUI, right-click the relevant pool and resize it dependingon how the new capacity will be split between any pools. If all the space on the XIV isdedicated to a single SVC then there must be only one pool.3. From the Volumes by Pools section of the XIV GUI, add new volumes of 1632 GB until nomore volumes can be created. (There will be space left over, which can be used as scratchspace for testing and for non-SVC hosts.)4. From the Host section of the XIV GUI, map these new volumes to the relevant SVCcluster. This completes the XIV portion of the upgrade.5. From the SVC, detect and then add the new MDisks to the existing managed disk group.Alternatively, a new managed disk group could be created. Remember that every MDiskuses a different XIV host port, so a new MDisk group ideally contains several MDisks tospread the Fibre Channel traffic.6. If new volumes are added to an existing managed disk group, it may be desirable torebalance the existing extents across the new space.To explain why an extent rebalance may be desirable, the SVC uses one XIV host port as apreferred port for each MDisk. If a VDisk is striped across eight MDisks, then I/O from thatVDisk will be potentially striped across eight separate I/O ports on the XIV. If the space onthese eight MDisks is fully allocated, then when new capacity is added to the MDisk group,new VDisks will only be striped across the new MDisks. If additional capacity supplying onlytwo new MDisks is added, then I/O for VDisks striped across just those two MDisks is onlydirected to two host ports on the XIV. This means that the performance characteristics ofthese VDisks may be slightly different, despite the fact that all XIV volumes effectively havethe same back end disk performance. The extent rebalance script is located here:http://www.alphaworks.ibm.com/tech/svctools8.11.2 Using additional XIV host portsIf additional XIV host ports are zoned to an SVC, then the SVC automatically rebalances itspreferences across all available XIV host ports (provided that we do not exceed the currentSVC limit of 16 WWPNs per WWNN). Depending on the number of modules in an XIV, not allChapter 8. SVC migration with XIV 273