US Patent 9880933 Distributed in-memory buffer cache system using buffer cache nodes

A separate distributed buffer cache system may be implemented for a storage client of a distributed storage system. Storage I/O requests may be sent from a storage client to one or more buffer cache nodes in a distributed buffer cache system that maintain portions of an in-memory buffer cache to which the requests pertain. The distributed buffer cache system may send the write requests on to the distributed storage system to be completed, and in response to receiving acknowledgements from the storage system, sending a completion acknowledgement back to the storage client. Buffer cache nodes may update buffer cache entries for received requests such that they are not available for reads until complete at the distributed storage system. For read requests where the buffer cache entries at the buffer cache node are invalid, valid data may be obtained from the distributed storage system and sent to the storage client.