PCIe (Peripheral Component Interconnect Express)
PCIe is a high-speed serial computer expansion bus standard used to connect hardware components — including NVMe SSDs — directly to a CPU. It provides dramatically higher bandwidth and lower latency than older bus standards like SATA or SAS.
PCIe and NVMe Storage
NVMe SSDs connect to the host via PCIe lanes. Where SATA maxes out at ~600 MB/s, a PCIe 4.0 ×4 NVMe drive reaches ~7 GB/s sequential throughput with latency under 50µs. PCIe 5.0 doubles that again.
PCIe Generations
- PCIe 3.0 — ~1 GB/s per lane. Most NVMe SSDs shipped 2015–2020.
- PCIe 4.0 — ~2 GB/s per lane. Mainstream since 2020; M.2 drives hit 5–7 GB/s.
- PCIe 5.0 — ~4 GB/s per lane. Enterprise SSDs reaching 12–14 GB/s sequential.
PCIe vs NVMe-oF
PCIe provides the local-attach path for NVMe storage. When storage is disaggregated via NVMe-oF, the PCIe bus on the storage node still connects local NVMe SSDs — the NVMe-oF target software then exposes those devices to remote initiators over TCP or RDMA at 25–40µs latency, only ~20µs higher than direct PCIe access.