Mat’s been doing some useful scripting again. This time it’s a small PERL script that identifies the allocation owner and default owner of a pool LUN on a CX4 or VNX and lets you know whether the LUN is “non-optimal” or not. For those of you playing along at home, I found the following information on this (but can’t remember where I found it). “Allocation owner of a pool LUN is the SP that owns and maintains the metadata for that LUN. It is not advised to trespass the LUNs to an SP that is not the allocation owner. This introduces lag. The SP that provides the best performance for the pool LUN. The allocation owner SP is set by the system to match the default SP owner when you create the LUN. You cannot change the allocation owner after the LUN is created. If you change the default owner for the LUN, the software will display a warning that a performance penalty will occur if you continue.”

There’s a useful article by Jithin Nadukandathil on the ECN site, as well as a most excellent writeup by fellow EMC Elect member Jon Klaus here. In short, if you identify NonOptimal LUN ownership, your best option is to create a new LUN and migrate the data to that LUN via the LUN Migration tool. You can download a copy of the script here. Feel free to look at the other scripts that are on offer as well. Here’s what the output looks like.