If you aren’t sure why one SSD costs vast amounts more than another, and you can’t find a straight answer on the product page, then you’ve come to the right place.
SSDs are such a key component in modern PCs and they come in many shapes and sizes. Not knowing the terms can leave you stranded with an SSD that cost you too much, or doesn’t offer you the performance boost you may have hoped for.
- HDD: Hard disk drives were the traditional storage medium on PCs for decades. The spinning platters store the data with a read arm scanning the surface to extract the information.
- SSD: Solid state drive uses non-volatile flash memory to store data, with much higher read and write speeds, but with no moving parts. It’s more expensive for lower capacities, but is (now) more reliable.
- Form Factor: 2.5", mSATA, M.2. PCIe, BGA.
- SATA: Interface for storage drives, currently utilises the AHCI protocol with a hard bandwidth limit of 600MB/s on inputs and outputs across the interface.
- PCIe: Interface used for the fastest consumer storage drives - can use AHCI and NVMe protocols.
- AHCI: Protocol - slow, designed for HDD - up to 600MB/s
- NVMe: Protocol - fast, designed for SSD - up to 3,500MB/s
Capacity: How much data can fit on the drive, measured in megabytes/gigabytes.
- NAND Flash: Type of non-volatile (retains information without power) memory cell used to store data, NAND refers to the type of logic gate used.
- SLC: A single layer cell stores one bit per cell and is accurate, fast, and long lasting - 90,000 to 100,000 life cycles. It operates in broader temperature range, but is more expensive than other alternatives.
- eMLC: Enterprise multi level cell is cheaper than SLC, delivers better performance and endurance compared to MLC - 20,000 to 30,000 life cycles.
- MLC: Multi level cell stores multiple bits of data on one cell (usually two) - lower cost of manufacturing than SLC, but a shorter life cycle, at around 10,000 life cycles - though is still more reliable than TLC.
- TLC: Triple level cell stores three bits of data per cell.It’s the cheapest to manufacture compared to MLC and SLC, but has a shorter lifespan compared to MLC - 3,000 to 5,000 life cycles.
- 3D NAND: Stacked flash memory has higher densities than 2D/planar NAND at a lower cost per bit - Samsung developed it as V-NAND (vertical NAND) - and it offers reduced power consumption, potentially higher capacity within a smaller area, and - increased reliability. - Unfortunately it also has increased costs to manufacture.
- 2D/planar NAND: Traditional NAND used in SSDs - reliability fell as interference between cells increased with density.
- 3D XPoint: This is Intel and Micron's non-volatile memory tech. It sits somewhere between your usual SSD NAND memory, and the DRAM found in your system memory, and offers incredibly low latency. It is still new to the SSD scene, yet Samsung are already offering an alternative in their V-NAND tech.
- Memory Controller: In charge of controlling read, write and erase cycles, wear levelling, garbage collection (clearing out-of-date data) and mapping. The memory controller is arguably the most important part of an SSD in terms of maintaining performance.
- Sequential read/write: How quickly the storage device can read/write a continuous block of data.
- Random read/write: How quickly the storage device can read/write random smaller blocks of data, we use 4kb files to benchmark the sort of file transfers an operating system will carry out during standard operation
- IOPS: Input/output operations per second - random/sequential also applies.