When I first time initialized a 1 TB LUN on an AX4, single controller no cache configuration, it took me 10 minutes. After using it for some time, we decided to unbind LUNs and create fresh LUNs, it now takes around 3 hrs and 45 minutes. I am using 750 GB SATA disks here.

EMC Support assumes that since the LUNs now had data on them, it should take long to initialize a LUN. How long...they don't know since they never do this?

Is this a good assumption OR could there be anything else responsible for this?