Padding synchronous write data with background write data based on storage system boundary alignment and size data

Abstract

The technology described herein is directed towards using background data to be written to a storage system as padding material that is combined with synchronous/client data writes to make data writes optimally-sized for the storage system. Instead of treating background work's data as a separate data stream of data to be written, some of the background data is preemptively maintained for padding the client I/O to optimal boundaries for a storage system. As a new client I/O data write comes in, prior to being written the system uses some of the preemptive padding to obtain an optimally-sized I/O data write. When that combined I/O operation completes, the client write is completed along with completing some amount of background data writing. Described are various ways to maintain the padding data store, as well as batching of some client I/O data received within a timeframe before writing.