NVRAM data organization using self-describing entities for predictable recovery after power-loss

摘要

In one embodiment, a parallel (e.g., tiered) logging technique is provided to deliver low latency acknowledgements of input/output (I/O) requests, such as write requests, while avoiding loss of data. Write data may be stored (copied) as a log in a portion of a dynamic random access memory and a non-volatile random access memory (NVRAM). The NVRAM may be configured as, e.g., a persistent write-back cache of the node, while parameters of the request may be stored in another portion of the NVRAM configured as the log (NVLog). The write data may be organized into separate variable length blocks or extents and “written back” out-of-order from the write-back cache to storage devices, such as SSDs, e.g., organized into a data container (intended destination of the write request). The write data may be preserved in the NVlog until each extent is safely stored on SSD.

主权项

1. A method comprising:
receiving at a storage system an input/output (I/O) request having a data and a parameter, wherein the storage system includes a volatile memory and a persistent memory; storing the data and the parameter in an entry of a log in the volatile memory, wherein the log is circular; updating a first pointer in the volatile memory, wherein the first pointer references the entry of the log in the volatile memory and wherein the first pointer further references an end of the log; copying the entry to the persistent memory; in response to copying the entry to the persistent memory, returning an acknowledgement to the I/O request; storing the data in one or more solid state drives (SSDs) attached to the storage system; and retiring the entry of the log in the persistent memory when the data is stored in the one or more SSDs.