Remap-Based Inter-Partition Copy for Arrayed Solid-State Drives

Abstract

The internal copy (IC) is a simple, yet powerful in-storage processing function, which changes the locations of data blocks without invoking any data transfer between the host and storage. Owing to the out-of-place update constraint of flash memory, solid-state disks (SSDs) employ a flash translation layer (FTL) to manage the logical-to-physical address translation. By leveraging the address indirection feature of SSDs, the IC can be processed only by remapping flash pages to new logical addresses without flash read/write operations. In the existing studies on remap-based IC, SSDs were assumed to have only a single FTL instance. However, recent large-capacity SSDs adopt an arrayed architecture including multiple FTL controllers, where each controller runs an FTL instance to manage its own partitioned address space. For the arrayed SSDs, inter-partition copy requests cannot be handled by address remapping because each partition is managed by a different FTL instance. In this study, we propose an inter-partition remap technique for IC-enabled arrayed SSDs. Additionally, we present the block allocation technique to minimize the number of inter-partition copy requests. Our proposed IC techniques were implemented on an actual arrayed SSD, and showed significant performance improvements compared to the previous remap techniques in several use cases.