Speculative Copying of Data from Main Buffer Cache to Solid-State Secondary Cache of a Storage Server

A method of operating a storage server, the method comprising:

• receiving read requests and write requests at the storage server from a client over a network;
• responding to the read requests and write requests, wherein responding to the write requests includes writing data blocks to a volatile main buffer cache of the storage server in response to the write requests;
• at a consistency point, writing the data blocks in the main buffer cache to a persistent storage subsystem of the storage server and thereafter marking the data blocks written to the persistent storage subsystem as clean;
• concurrently with responding to read requests and write requests from the client, copying data blocks marked as clean to a secondary cache implemented in solid-state memory, before there is a need to evict data from the main buffer cache;
• and
• evicting from the main buffer cache data blocks that have been copied to the secondary cache, wherein said evicting is not a response to the copying of data blocks to the secondary cache.

A network storage system comprising:

• a network interface through which to communicate with a set of clients over a network;
• a storage interface through which to communicate with a persistent storage subsystem of the storage system;
• a main buffer cache, to cache data read from and data to be written to, the persistent storage subsystem;
• a secondary cache implemented in non-volatile solid-state memory, to cache data initially stored in the main buffer cache;
• and
• a storage manager to service read and write requests from the clients, including writing data to the main buffer cache and thereafter copying data from the main buffer cache to the persistent storage subsystem at a consistency point, wherein the storage manager further is to mark the data as clean when the data has been copied to the persistent storage subsystem, wherein the storage manager further is to reduce the likelihood of bursts of writes to the secondary cache by copying data marked as clean in the main buffer cache to the secondary buffer cache before there is a need to evict the data from the main buffer cache.