SSD performance at a glance

NVMe is a storage protocol designed specifically with SSDs in mind. With the elimination of the intermediating SATA HBA layer, NVMe allows SSDs to communicate directly with the CPU via the PCIe bus, opening channels for ground-breaking performance improvements. To put it into perspective, the performance limit of the SATA III bus is 6Gb/s, meaning a SATA SSD can offer a max of 550MB/s of throughput after overhead. A single PCIe 3.0 lane can offer 1GB/s (bidirectional) of throughput, so a PCIe 3x4 SSD can reach a throughput of up to 4GB/s read/write. That goes up to 8GB/s (bidirectional) for PCIe Gen 4X4 SSDs. The performance limitation here moves from the protocol to the NAND media, which has been undergoing tremendous development in recent years, allowing manufacturers to squeeze the highest density and performance into the smallest form factors.

Protocol latency is also greatly reduced with NVMe due to the shortened and optimised datapath, allowing lower latency than SATA/SAS. The management of queues in NVMe devices is also handled more efficiently by the CPU due to the I/O processing doorbell signalling which significantly reduces CPU overhead. In addition, NVMe devices are supported by most major operating systems due to the massive development effort carried out in the past decade.

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