If you are using an EMC CX storage array, and you plan on using MirrorView to replicate data between two storage arrays there are a few catches which you need to keep in mind that aren’t all that obvious unless you read through literally hundreds of pages of documentation.
When you go to use MirrorView the ports which you will be using have been defined already, and can not be changed without resetting the entire storage array. Now depending on what hardware is installed when the array is first powered up this will determine which port you can use for MirrorView.
If you have the base cards which come with the system, then FC0 will be the port which is used for MirrorView. If you have an expansion fiber card installed in the system, then port FC4 (the port labeled 0 on the expansion card) is the port which will be used. Now, the catch here is that FC0 will be a 4 Gig port. Currently with the newest CX4 arrays you can’t change the cards which the system ships with from 4 gig to 8 gig ports. So if after time you find that you need more bandwidth between the arrays for Mirrorview, pretty much your only option is to move your hosts off of the FC0 port. If the only thing using FC0 is MirrorView and you still need more bandwidth you’ll need to contact EMC support and work with them to come up with a solution short of resetting the array to the same state you received it in.
Now the same applied to the iSCSI MirrorView port. If you get the array with no expansion cards, the iSCSI port with be port 0. If you get the array with an iSCSI expansion card installed on first power up then iSCSI port 3 (the port labeled 0 on the expansion card) will be your iSCSI MirrorView port.
Now another catch that you may not be aware of, MirrorView is SP specific. So if your LUN is hosted by SPA which you setup the MirrorView replication it has to go to SPA on the remote array. Now if your LUN trespasses to the other SP, the MirrorView replication will stop until the LUN moves back to the hosting SP. If you need to move the LUN to the other SP, then you’ll need to remove MirrorView from the LUN and reset it back up.