SoftwAre Log-Structured Array (SALSA) – A unified stack for SSDs and SMR disks

Software-defined, cost-competitive storage that is based on commodity hardware is becoming increasingly important in modern data centers. We present SoftwAre Log-Structured Array (SALSA), a unified software stack that manages low-cost Flash-based SSDs as well as SMR hard disks. SALSA elevates the performance and endurance of low-cost, commodity Flash SSDs to meet the requirements of data centers for certain classes of workloads. In addition, SALSA enables SMR hard disks to be accessed over the traditional block interface with increased performance, allowing them to be used as a drop-in replacement for conventional hard disks. SALSA employs software intelligence to transform the user access patterns to be as friendly as possible for the underlying storage medium. By moving complexity from hardware to software, in combination with data reduction and data segregation techniques, SALSA reduces storage costs substantially. Our experimental results indicate order-of-magnitude improvements with SALSA on top of commodity drives, making it a very promising approach for low-cost, software-defined storage.