If you are using VMware only <2TB per LUN is supported. If you got a LUN larger than that, only space above the intitial 2TB is visible. 2,5TB for example only shows 0,5TB... 4,1TB only shows 0,1TB (2TB + 2TB + 0,1TB). Split the storage into <2TB LUNs and you are ready to go.
Thanks! I am using Citrix Xenserver 5.5. The reason why it did that is because lvg00 wasn't fully initialized. Once it was, Xenserver began to see the full 4TB.