By using a size over 1,5 GB i can see the LUN, so problem is that i cannot creat a LUN smaller than 1,5GB.
All our storage guys are out of house so i don't know if this limitations is on purpose but it's ok for me, you just need to know 
But i'm no longer sure if my way of setting up a shared storage is right?
Is there a way i can present this LUN as a storage to two VM's. Both are in a running state.
I followed the steps in "Setup for Failover Clustering and Microsoft Cluster Service ESXi 5.1" but still getting an error when i start second VM.
Do i need to clone the second Vm from first one and cluster this two vm's
I also tried the steps with RDM but i get the same error.
btw, thx for helping me