The present invention relates to compounds of formula useful as selective inhibitors of JAK2 kinase. The virtual block device interacts with additional elements to do data deduplication to files at the block level such that one or more files accessed using the virtual block device have at least one block which is shared by the one or more files. Additionally, the system further comprises at least one extra surface parallel to the second lens surface, wherein at least one extra surface has a length L and is parallel to each other.