I understand that hard drives use spinning platters, but I'm unclear about SATA SSDs. Do they use essentially the same flash-memory technology as NVMe drives, with the main speed difference coming from the connection and protocol? Or are there important differences in how the drives themselves read and write data?
3 Answers
SATA SSDs are still dramatically faster than hard drives because they have no moving parts and much lower access latency. Even though both SATA hard drives and SATA SSDs use the same SATA interface, the SSD can respond far more quickly; the interface mainly prevents it from reaching the higher speeds available to NVMe drives.
A SATA III connection tops out at 6 Gb/s, which works out to roughly 500–550 MB/s after overhead. NVMe drives use multiple PCIe lanes, giving them much more bandwidth and allowing many commands to be processed in parallel. That is why NVMe drives can be several times faster, especially for large transfers and demanding workloads.
SATA SSDs and NVMe SSDs generally use the same basic NAND flash storage technology. The biggest difference is how they communicate with the computer: SATA SSDs use the SATA interface and the older AHCI protocol, while NVMe drives communicate directly over PCIe using a protocol designed for flash storage. SATA SSDs can therefore be installed in many systems that originally used a SATA hard drive, but they remain limited by the SATA connection.
So the main limitation is basically the way the drive connects and communicates with the computer, rather than the flash memory itself?