US Patent 9251064 NVRAM caching and logging in a storage system

In one embodiment, a node coupled to one or more solid state drives (SSDs) executes a storage input/output (I/O) stack having a plurality of layers, including a persistence layer. The node includes a non-volatile random access memory (NVRAM). A portion of the NVRAM is configured as a write-back cache to store write data associated with one or more write requests. The persistence layer is configured to organize the write data into extents that are written back to the one or more SSDs in any order. The write data is preserved in the write-back cache until each extent is safely and successfully stored on the one or more SSDs in an event of a power loss.