In terms of thick/thin confirmation, is that a setting in VMware? If so, then i used the thick one - one that allocates the total amount of space to the hard-drive (not the salable one that takes up less space - which may be slower). When i was diagnosing this issue about 1 year ago on my server, i believe that i tried all possible configurations, but wasn't able to get speeds about 60-70MBps - i think the issue wither the ESXi 5.0 P400 drivers or the p400 itself. I believe that these 2Tb WD RE4 64Mb cache hard-drives should be performing better than that, especially in raid10 setting!
I may get the P410 controller so i'll have a single 4Tb volume instead of 2 x 2Tb volumes that i had to create in the ESXi in order to use the space... i wonder if because ESXi sees it as 2 datastores of 2Tb each, maybe that's why it's slower... who knows.
Thanks