The SSD Deep Dive

• SSD speed can be confusing because it depends on a few things
  • The connector and connector generation
    • The form-factor does not always correlate to the connector type
  • The storage type
  • The storage layers

A matrix overview of SSD storage types and form factors

The connector:

• SATA III (can be M.2 form factor) is the same as used by most HDDs and tops out at ~600MB/s
• PCIe (can be M.2 form factor or use PCIe lanes directly)
  • PCIe 3 reaches ~985MB/s
  • PCIe 4 reaches ~2000MB/s
  • PCIe 5 reaches ~12000MB/s

The storage type:

• SATA
• NVME

The storage layers:

Remember that certain voltage applied to or removed to/from each cell?

• Some drives will use a different number of layers of voltage (SLC/MLC/TLC/QLC)
  • More layers means slower, more unreliable drives, and lower lifetimes
  • Higher layer counts are less expensive
  • Like with CMR and SMR, manufacturers publish this, but it’s not necessarily easy to find

image credit binarytides.com