Methods, apparatus, and computer-accessible storage media for optimizing block storage I/O operations in a storage gateway. A write log may be implemented in a block store as a one-dimensional queue. A read cache may also be implemented in the block store. When non-ordered writes are received, sequential writes may be performed to the write log and the data may be written to contiguous locations on the storage. A metadata store may store metadata for the write log and the read cache. Reads may be satisfied from the write log if possible, or from the read cache or backend store if not. If blocks are read from the read cache or backend store to satisfy a read, the blocks may be mutated with data from the write log before being sent to the requesting process. The mutated blocks may be stored to the read cache.