1. An apparatus, comprising: non-transitory storage media configured as a cache associated with a physical computing machine that shares access to a block storage device with at least one other physical computing machine; a caching logic associated with the physical computing machine, the caching logic configured to cache data in the cache, wherein the caching logic caches data stored in a delegated range of memory blocks and does not cache data stored outside of the delegated range of memory blocks; a block delegation logic configured to: determine whether a virtual machine has moved to the physical computing machine from the at least one other physical computing machine; revoke a caching right associated with the at least one other physical computing machine upon a determination that the virtual machine has moved to the physical computing machine, wherein the caching right is an exclusive right granted to the caching logic; assign, to the physical computing machine, a new caching right for the delegated range of memory blocks in the block storage device to the caching logic.