March 28, 2011, 10:27 AM — We live in a world fuelled by data, and PCs and modern digital gadgets need to store their data somewhere. Data is stored inside a PC, laptop or similar device, and is often expanded with external storage for backups or simply to expand on internal capacity.
[ See also: USB 3.0 vs. eSATA: Is faster better? ]
Until relatively recently, nearly all data was stored on hard disks. These come in two main types: 3.5in Serial Advanced Technology Attachment (SATA) disks, most often used in full-size desktop PCs; and 2.5in SATA disks, fitted to notebook PCs.
The 3.5in disk is evidently physically larger, but will be cheaper, when comparing capacity, to 2.5in hard-disk dirves (HDD).
The 3.5in HDD is also generally available in larger capacities: in March 2011, 3.5in disks are available in capacities up to 3TB, while 2.5in drives are usually available in capacities only up to 1TB.
The 2.5in disk runs cooler and quieter than the 3.5in disk, but is also slower to access data. Rotational spindle speed of most 2.5in disks is 5400rpm, although 7200rpm versions also available for higher performance applications.
Most 3.5in disks run at 7200rpm, with some low-power 'green' drives designed to run around 5400-5900rpm.
See all: Internal hard drives reviews
Gradually replacing the HDD is the solid-state drive (SSD). This uses NAND flash solid-state memory, and is now available in 2.5in SATA form factors up to 512MB capacity - at a price. Most practical SSDs are sized from 60GB to 256GB.
SSDs are faster than most HDDs, whether looking at read/write speeds or response time (latency). They run silent and are resistant to shock.
See all: Solid-state drives reviews
When looking at either hard-disk or solid-state internal storage, look at the generation of the SATA bus. The later versions are faster.
First generation SATA had a nominal transfer speed of 1.5 gigabit per second (Gb/s); second generation SATA - the most common type in use in 2011 - is specified to 3Gb/s.
The latest storage devices and PCs are built to SATA 6Gb/s specifications.
These three generations of SATA are sometimes erroneously referred to as SATA 1, 2 and 3; or I, II and III. To avoid confusion (such as SATA 3Gb/s vs SATA 3) we always use the transfer speed to pinpoint SATA version.