1. A coordinator node apparatus for operating on data blocks comprising: a first interface, connected to a Level 2 (L2) cache storage endpoint over a first network connection; a second interface, connected to cloud storage over a second network connection, the first and second network connections further such that a physical distance between the coordinator node and the L2 cache storage endpoint is shorter than a physical distance between the coordinator node and the cloud storage; a local Level 3 (L3) cache storage; and a processor for responding to a block write request from the L2 cache storage endpoint as a write back cache, by acknowledging the block write request to the L2 cache storage endpoint even if a data block associated with the write request is not presently stored in the local L3 cache storage; storing the data block and metadata associated with the block write request in the local L3 cache storage, before forwarding the data block and metadata associated with the block write request to the cloud storage; maintaining a global logical block address (LBA) metadata map; and distributing the global LBA metadata map to the L2 cache storage endpoint and to the cloud storage.