Thanks for the replys, I've always linked IO reads to performance, so i was very confused when i saw a solution generating higher IO and still performing way better, yes I'm using a SQL Server 2008 and I would love to get my hands into changing that field to a HierarchyID but i'll have to study impacts that could cause on existing code so for now i'll ride with a rCTE, I'm aware this is already a bit off the topic, but anyone could point some read (book,blog,alikes) so I could take better grasp with IO / Performance relationship so I won't get frustated again with IO? Thanks Guys !