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.
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.
Outside of your PC or digital device, data can be either directly attached and stored locally on a desktop or portable drive; or on a local network; or beyond the local network on what is colloquially termed ‘the cloud’.
Direct-attached storage (DAS)
For best GB-per-pound, the desktop hard drive with 3.5in is the most cost effective. The disadvantage is a slightly larger and noisier external drive, and one that will require its own mains power, usually with a wall-wart-style power supply.
Laptop users or those wanting to free the desk of large drives and more mains wires may prefer an external drive using a 2.5in notebook drive. These are much more compact, but maximum storage is limited to typically 750GB, sometimes 1TB, and price is commensurately higher.
See all: Portable hard drives reviews
See all: USB drives
There are several ways to directly connect a drive to a laptop or desktop PC. By far the most common is USB 2.0. This also provides the necessary power (‘bus power’) for most portable drives too.
The USB 2.0 standard is somewhat slow by today’s standards. The nominal transfer speed is 480 megabits per second (Mb/s) but don’t be fooled by this spec – actual transfer speed is closer to 240Mb/s.
(Note that data transfer is usually expressed in megabytes per second (MB/s), where 1 Byte equals 8 bits.)
FireWire is available in two version: the original Firewire 400, specified for 400Mb/s operation, and FireWire 800, to 800Mb/s. These equate to real-world figures of around 280Mb/s and 720Mb/s.
USB 3.0 is now becoming more popular, with a spec that promises 4.8 gigabit per second (Gb/s) operation. Again, expect real-world through put to be much slower, although even half that speed represents 300MB/s, which is in line with the speed of a good modern SSD.
Another high-speed connection type to look out for is eSATA, an external version of SATA with the same potential speed as the internal version (although not to SATA 6Gb/s at present).
The fastest connection type just launched is Thunderbolt, formerly known as Light Peak. This is only present on Apple MacBook Pro notebooks at present, and external drives to support the format will not be ready until later in 2011. Thunderbolt promises speeds of two channels of 10Gb/s, in both directions at the same time.
Network-attached Storage (NAS)
A network-attached storage (NAS) drive is simply storage such as one or more hard disks in a single box, connected to a network and accessed like a data server.
Consumer NAS drives tend to have just one or two hard disks, and low-power processors in order to keep cost and heat/noise down. These will tend to be slower when accessing data, especially in write speed performance.
Business and professional NAS drives typically have four, six or more hard disks, configured in a system known as Redundant Array of Independent Disks (RAID).
Different types of RAID array are available, and the user usually needs to set up as required before use.
See all: Network storage reviews
Common RAID configurations
RAID 0 is often used in performance applications. Typically, two disks are ‘striped’ together to create a total capacity the sum of the two disks. If one drive fails, all data is lost.
RAID 1 provides good security for data, by mirroring the same data on two drives. Total available storage is equal to the size of one disk.
RAID 5 combines some of the speed of RAID 0 with the security of RAID 1. You need three or more drives. If one drive fails, data is preserved although you should replace this drive immediately in order that the NAS unit can reconstruct redundant data across the array.
RAID 6 is like RAID 5, but allows for the failure of up to two disks at the same time. Requires four or more disks to configure.
As well as providing a simple repository for storing data, NAS drives can also be configured for a multitude of everyday applications. These include FTP server, iTunes or media server for home entertainment devices. Setup can be far more complex than simply plugging into a PC though. Most NAS drives are configured through a webpage interface.
Most people already use cloud storage, in the form of popular free email services such as Googlemail or Hotmail. Your email is stored on a remote server, and accessed by your PC, laptop or smartphone over the internet, on demand.
Cloud storage is also offered by some companies to store your other personal or business data; for example, automated remote backup such as Carbonite, Mozy, or Dropbox. Such services typically use encryption to safeguard personal data in transit. Operation is slow, limited principally by the slow upload speeds of most people’s ADSL braodband connections (circa-0.5-1Mb/s).
See all: Storage reviews