SSD (Solid State Drive)
An SSD is a storage device that uses NAND flash memory to store data persistently, with no moving parts. Unlike HDDs, SSDs provide microsecond-level access latency, hundreds of thousands of IOPS, and high resilience to shock. NVMe SSDs connected via PCIe are the highest-performance class of SSD.
SSD vs HDD
HDDs use spinning magnetic platters and a mechanical read/write head — random access latency is 5–10ms and they deliver ~150 random IOPS. SSDs have no moving parts: read latency is 50–150µs and modern NVMe SSDs sustain 1–7 million random IOPS.
SSD Interface Types
- SATA SSD — Uses legacy SATA interface (600 MB/s max). Uses AHCI protocol. Slowest class of SSD.
- SAS SSD — Higher reliability SCSI interface. Common in enterprise servers before NVMe.
- NVMe SSD (PCIe) — Connects via PCIe, uses NVMe protocol. Sub-50µs latency, millions of IOPS. The modern standard for performance storage.
NVMe SSDs and NVMe-oF
In a disaggregated NVMe-oF deployment, NVMe SSDs sit in dedicated storage nodes and are exposed to compute nodes over the network. The compute node's OS sees the remote NVMe storage as a local block device, achieving latency of 25–40µs — just 20µs above direct PCIe access — while gaining HA, replication, and independent scaling that local SSDs cannot provide.