IBM XIV Storage System Copy Services and Migration

LUN0There is a requirement for the EMC Symmetrix or DMX to present a LUN ID 0 to the XIV inorder for the XIV Storage System to communicate with the EMC Symmetrix or DMX. In manyinstallations, the VCM device is allocated to LUN-0 on all FAs and is automatically presentedto all hosts. In these cases, the XIV connects to the DMX with no issues. However, in newerinstallations, the VCM device is no longer presented to all hosts and therefore a real LUN-0 isrequired to be presented to the XIV in order for the XIV to connect to the DMX. This LUN-0can be a dummy device of any size that will not be migrated or an actual device that will bemigrated.LUN numberingThe EMC Symmetrix and DMX, by default, does not present volumes in the range of 0 to 512decimal. The Symmetrix/DMX presents volumes based on the LUN ID that was given thevolume when the volume was placed on the FA port. If a volume was placed on the FA with aLUN ID of 90, this is how it is presented to the host by default. The Symmetrix/DMX alsopresents the LUN IDs in hex. Thus, LUN ID 201 equates to decimal 513, which is greater than512 and is outside of the XIV's range. There are two disciplines for migrating data from aSymmetrix/DMX where the LUN ID is greater than 512 (decimal).Re-map the volumeOne way to migrate a volume with a LUN ID higher than 512 is to re-map the volume in one oftwo ways:► Map the volume to a free FA or an FA that has available LUN ID slots less than hex 200(decimal 512). In most cases this can be done without interruption to the productionserver. The XIV is zoned and the target defined to the FA port with the lower LUN ID.►Re-map the volume to a lower LUN ID, one that is less than 200 hex. However, thisrequires that the host be shut down while the change is taking place and is therefore notthe best option.LUN-OffsetWith EMC Symmetrix Enginuity code 68 - 71 code, there is an EMC method of presentingLUN IDs to hosts other than the LUN ID given to the volume when placed on the FA. In theSymmetrix/DMX world, a volume is given a unique LUN ID when configured on an FA. Eachvolume on an FA must have a unique LUN ID. The default method (and a best practice ofpresenting volumes to a host) is to use the LUN ID given to the volume when placed on theFA. In other words, if 'vol1' was placed on an FA with an ID of 7A (hex (0x07a) decimal 122),this is the LUN ID that is presented to the host. Using the lunoffset option of the symmaskcommand, a volume can be presented to a host (WWPN initiator) with a different LUN ID thanwas assigned the volume when placed on the FA. Because it is done at the initiator level, theproduction server can keep the high LUNs (above 128) while being allocated to the XIV usinglower LUN IDs (below 512 decimal).Migrating volumes that were used by HP-UXFor HP-UX hosts attached to EMC Symmetrix there is a setting known asVolume_Set_Addressing that can be enabled on a per-FA basis. This is required for HP-UXhost connectivity but is not compatible with any other host types (including XIV). IfVolume_Set_Addressing (also referred to as the V bit setting) is enabled on an FA, then theXIV will not be able to access anything but LUN 0 on that FA. To avoid this issue, map theHP-UX host volumes to a different FA that is not configured specifically for HP-UX. Then zonethe XIV migration port to this FA instead of the FA being used by HP-UX.MultipathingThe EMC Symmetrix and DMX are active/active storage devices.Chapter 7. Data migration 225