June 9, 2015

EMC VNX : Lun Migration

LUN Migration is a feature available from Flare Code Release 16 onwards. LUN Migration moves data from one LUN to another LUN within a clariion storage array without affecting the production.
 
Why LUN Migration?
LUN Migration might be an instance where we may want to offload a LUN from a busy Raid Group/Heavily Utilized pool for performance issues. Or, we want to move a LUN from SATA Drives to FC Drives and vice-versa.

LUN Migration Rues
  • LUN Migration can be done from any RAID type to any RAID type, same drive type or different drive type.
  • LUN Migration can be possible from a thick LUN to a Thin Lun or vice-versa.
  • Destination LUN can be on a different Raid Group, on a different BUS, on a different Enclosure.
  • LUNs should not private LUNs or Hot Spares. 
  • LUNs should not be transitioning, binding, expanding, or migrating state.
  • LUNs can be metaLUNs.
  • Destination LUN should not be in a Storage Group. 
  • Destination LUN should not be part of SnapView or MirrorView operations. 
  • Destination LUN should be larger than Source LUN. 

LUN Migration Process
The migration process is actually a two-step process. It is a copy first, then a move. Once the migration begins, it is a block for block copy from the Source LUN (Original Location) to the Destination LUN (New Location). This is important to know because the Source LUN does not have to be offline while this process is running. The host will continue to read and write to the Source LUN, which will write to Cache, then Cache writing out to the disk. Because it is a copy, any new write to the source lun will also write to the destination lun. At any time during this process, you may cancel the Migration if the wrong LUN was selected, or to wait until a later time. A priority level is also available to speed up or slow down the process.

LUN Migration Steps
STEP 1: Log into Unisphere and then go to Storage and select LUNs.
STEP 2: Create a new LUN that is equal or larger in size than the source LUN.


STEP 3: Right click the source LUN and select Migrate.


STEP 4: Select the destination LUN and the migration rate.


STEP 5: LUN migration should now be started. You can monitor the status by selecting "LUN Migration Summary" on the right hand side.


STEP 6: (Optional) To change the migration rate, go to the Migration tab under the LUN properties. This tab will only be visible when there's a LUN migration currently running. 

After Migration Completes
Once the LUN migration is complete, the source LUN is deleted and the new destination LUN will be exactly the same as the previous source. This means the Source LUN will occupy the space of the Destination LUN, taking with it the same LUN ID, SP Ownership, and host connectivity. The only things that may or may not change based on your selection of the Destination might be the Raid type, Raid Group, size of the LUN, or Drive Type.

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