After re-arranging the LUNs to separate targets I can't have my datastore mounted correctly by VMware.
Sulution:
The problem is caused by UID's. When UID of discovered target doesn't match the actual UID VMware considers it as a shapshot.
To solve this issue force mount the target by it's vmfs volume name.
Here you can find more datailed information how to do it:
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1011387
