Write type based crediting for block level write throttling to control impact to read input/output operations

Abstract

A technique manages bandwidth allocated among input/output operations, such as reads and writes, to storage devices coupled to storage nodes of a cluster. The technique balances the writes in a manner that reduces latency of reads, while allowing the writes to complete in a desired amount of time. The writes include write types, such as client writes, data migration writes, block transfer writes, and recycling writes, which are defined by differing characteristics and relative priorities. To ensure timely completion of the write types, the technique provides periodic time intervals over which the writes may be balanced and allocated sufficient bandwidth to access the storage devices. The time intervals may include shuffle intervals within a larger distribution interval. In addition, the technique throttles certain write types at the storage device level to maintain consistent read performance. Throttling is based on a credit system that allocates bandwidth as 'credits' based on write type.