LUNs on a storage system represent the blobs of storage that are allocated to a server. A (VNX) storage admin creates a LUN on a RAID Group or Storage Pool and assigns it to a server. The server admin discovers this LUN, formats it, mounts it (or assigns a drive letter) and starts to use it. Storage 101. But there’s more to it than just carving out LUNs from a big pile of Terabytes. One important aspect is LUN ownership: which storage processor will process the I/O for that specific LUN?!
When migrating servers from one storage system to another there are basically two options: Migrate using storage features like SAN Copy or MirrorView, or migrate using server based tools like PowerPath Migration Enabler Host Copy, VMware Storage VMotion or Robo Copy. Which option you choose depends on a lot of factors, including the environment you’re in, the amount of downtime you can afford, the amount of data, etc. I’ve grown especially fond of PowerPath Migration Enabler due to its ease of use. You can throttle its migration speed, your “old” data is left intact (so you’ve got a fallback) and once you’ve gotten use to the commands it’s child’s play to migrate non-disruptively and quickly.