Is it possible to use optimizer migrate to move thin devs to thick on a dmx-4

symmetrix optimizer can not do that. it move/swap hypers for performance perspective only. if you're on DMX with 5773 or lower.  you're unable to peform the thin to thick replication.

I've never used symopt and I have a question: does it only move hypers (slices) or does it move the entire symdev?

Yes, it moves highly active hypervolumes on higher active disk to lower active disk for balancing the workload. it bases on the hypervolume on single physical disk but not symdev level.

I specifically asked, because tons of people say hyper (part of a symdev) when they actually mean symdev (maskable device)

People are using it incorrectly, that's what's wrong!

SAN or Storage, make your choise, but don't say SAN when you mean Storage!

Gigabyte or Gibibyte, the first is 1,000,000,000 and the binary one is 1024x1024x1024.

http://en.wikipedia.org/wiki/Gigabyte --> look in the table on the right!

It's not difficult, simply say what you mean using the official standards and don't assume everybody else is on the same page as you. Assumption is the mother of... you know the rest.

yes, the name sometime is little confusing

Just created a little blog post on the subject on www.50mu.net