Glossary

NVMe (Non-Volatile Memory Express)

NVMe (Non-Volatile Memory Express) is the protocol servers use to communicate with flash storage over PCI Express, the high-speed bus that links devices directly to the processor. Designed for flash rather than spinning disks, it handles many requests in parallel, which cuts latency and raises the number of operations a drive can serve.

Built for flash, not disks

SATA and SAS were designed for spinning disks that serve one request at a time, so they funnel commands through a single queue and a controller in between. Flash chips can work on many requests at once and were left waiting. NVMe gives each processor core its own queues straight to the drive, so requests are submitted and completed in parallel without contending for a shared path. The gain shows most in random workloads, counted as IOPS, and in latency under load.

Where the bottleneck goes next

Faster drives do not always produce faster applications, because the drive is one link in a chain. The fastest current NVMe drives can each read data at roughly the rate a 100 Gb/s network port carries it, so a server holding several of them can saturate its network and processors well before the flash is busy. After a move to NVMe, the limit usually shifts to the network, the CPU or the storage software. Storage throughput is a property of the whole path, not of the drive.

Datasheet figures and steady state

Published drive figures are typically measured on new, empty drives, where no background housekeeping competes with the host. Once a drive has been filled and overwritten, garbage collection runs alongside host requests and performance settles lower. Results taken in steady state, after the whole drive has been written over, describe production behavior. Method is covered under storage benchmarking.

Where NVMe appears

  • Inside servers, as local drives.
  • In an all-flash array, as the link between controllers and drive shelves.
  • Across a network, where NVMe over Fabrics carries the same commands to flash in another enclosure.
  • Under scale-out storage nodes that keep metadata and active data on NVMe while bulk data sits on cheaper media.

NVMe names how a drive is reached, not what holds the data. That remains NAND flash inside an SSD.