Selective Power-Loss-Protection Method for Write Buffer in ZNS SSDs

Most SSDs (solid-state drives) use an internal DRAM (Dynamic Random Access Memory) to improve the I/O performance and extend SSD lifespan by absorbing write requests. However, this volatile memory does not guarantee persistence of buffered data in event sudden power-off. Therefore, highly reliable enterprise employ power-loss-protection (PLP) logic ensure durability using back-up power capacitors. The must provide enough capacitors for PLP proportion size buffer. Meanwhile, emerging ZNS (Zoned Namespace) are attracting attention because they can support many streams that useful multi-tenant systems. Although do mapping table unlike conventional block-interface SSDs, a large buffer is required streams. reason each stream needs its own buffering where host allocate separate zones different Moreover, larger capacity more supports, required. depends on amount capacitance, which limited only space, but also cost. paper, we present set techniques significantly reduce capacitance while ensuring during First, note modern file systems or databases have their solutions recovery, such as WAL (Write-ahead Log) journal. propose selective method ensures journal entire data. Second, minimize time taken PLP, balanced flush temporarily writes multiple maximize parallelism preserves original location when restored. proposed methods implemented evaluated modifying FEMU (QEMU-based Flash Emulator) RocksDB. According experimental results, selective-PLP reduces 50 90% retaining reliability SSDs. In addition, latency up 96%.