I/O in a Flash: Evolution of ONTAP to Low-Latency SSDs

Flash-based persistent storage media are capable of submillisecond latency I/O. However, a storage architecture optimized for spinning drives may contain software delays that make it impractical for use with such media. The NetApp ® ONTAP ® storage system was designed originally for spinning drives, and needed alterations before it was productized as an all-SSD system. In this paper, we focus on the changes made to the read I/O path over the last several years, which have been crucial to this transformation, and present them in chronological fashion together with the associated performance analyses.