## 4.3 Hard drives: HDD vs SSD

Unless you have a fairly expensive laptop your computer probably has a standard hard disk drive (HDD). HDDs were first introduced by IBM in 1956. Data is stored using magnetism on a rotating platter, as shown in Figure 4.2. The faster the platter spins, the faster the HDD can perform. Many laptop drives spin at either $$5400$$RPM (Revolutions per Minute) or $$7200$$RPM. The major advantage of HDDs is that they are cheap, making a $$1$$TB laptop standard.

Solid state drives (SSDs) can be thought of as large, but more sophisticated versions of USB sticks. They have no moving parts and information is stored in microchips. Since there are no moving parts, reading/writing is much quicker. SSDs have other benefits: they are quieter, allow faster boot time (no ‘spin up’ time) and require less power (more battery life).

The read/write speed for a standard HDD is usually in the region of $$50-120$$MB/s (usually closer to $$50$$MB). For SSDs, speeds are typically over $$200$$MB/s. For top-of-the-range models this can approach $$500$$MB/s. If you’re wondering, read/write speeds for RAM is around $$2-20$$GB/s. So at best SSDs are at least one order of magnitude slower than RAM, but still faster than standard HDDs.