Storage
SSD, NVMe & HDD
The three storage media tiers: HDD (cheap, slow spinning disks), SSD (fast flash), and NVMe (fastest flash over a direct bus).
These are the three speeds of storage. HDDs are spinning magnetic disks, cheap per terabyte and slow, still fine for cold archives and backups. SSDs are flash memory with no moving parts, many times faster, now the default for most cloud volumes. NVMe is flash again, but wired over a direct PCIe bus that removes the old SATA bottleneck, so it's faster still.
The difference shows up under random access, which is exactly what databases and busy applications generate. An NVMe-backed database can serve queries a database on an HDD would choke on. Providers like Vultr and Hetzner advertise NVMe on their higher tiers precisely because it's a real, measurable win for the workloads people care about.
For a typical site the storage medium rarely bottlenecks anything, so paying up for NVMe is wasted. For a write-heavy database or an I/O-bound app, it can be the single best money you spend.