Buy Smarter: what you need to know about... optical disc drives
Laser sharp storage
Buyer's Guide Optical drive is the collective term for CD, DVD and Blu-ray readers, recorders and rewriters, the mainstay of swap-in-swap-out storage in notebook and desktop computers.
At its simplest, an optical disc can load applications or play music or films, and at its most complex, in the form of a dual-layer, Blu-ray BD-RE disc, it can play high-definition (HD) movies and record up to 50GB of data.
You may be wanting to upgrade an optical drive, or move from CD to DVD or DVD to Blu-ray, or you may want to add an extra drive to a machine with a spare bay. Whatever it is, there is a variety of drives to choose from.
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Optical drive types
You will find it increasingly difficult to buy a CD-only drive, as effectively all DVD drives play all varieties of CD in addition to handling a range of DVD types. Blu-ray drives can similarly read, and usually write, both DVDs and CDs.
Upgrade your desktop's internal optical drive for greater capacity storage and HD playback
There is only one type of recordable and one type of rewriteable CD, but there are two complementary standards of DVDs: DVD+R/RW and DVD-R/RW. These DVD-plus and DVD-minus formats are distinct, but most modern drives can read and write both of them.
The rewriteable Blu-ray drive uses the abbreviation BD-RE, rather than BD-RW, as the drive has to be fully Erased before rewriting.
DVD drives are available as standard 3.5in internal and half-height, laptop-style devices. Both of these can also be had as external drives in separate enclosures, linked via USB, Firewire or eSATA cables.The Samsung Ultra-Slim AA-ES3P95B  charges easily using one USB cable and has a hidden power cord. If you are after an external drive, make sure you get the appropriate type for the connection you have available.
Optical Disc Formats
There are two types of DVD disc which don’t get the exposure they deserve. DVD-Ram is a rewritable 4.7GB disc which to Windows machines looks like a high-speed, high-capacity floppy. Once fitted, no special software is needed to write to and read from the device.
The duty cycle of a DVD-Ram disc is much higher than for DVD±RW and is often rated at 100,000 read/writes. DVD±RW typically supports about 1,000 read/writes.
DVD-Ram is a useful alternative to the more commonplace DVD±RW format
Another more recent DVD format is M-Disc. This relies on special media, which its maker, Milleniata , claims is capable of taking permanent engraving of data. Regular DVDs rely on changes in dyes laminated in plastic to distinguish data '0's from '1's but these dyes degrade over time, making them unsuitable for long-term archival data.
M-Disc uses write-once discs but the "inorganic rock-like data layer" is physically engraved by a high-temperature laser. It requires a compatible drive to burn an M-Disc, and there are several LG models available which don’t attract a premium price. Once burnt, the discs can be read on any reasonably up-to-date DVD or Blu-ray drive.
Optical drive speeds
Rather confusingly, optical drive speeds are quoted in multiples of a base speed. So you get 2x, 8x, 52x drives and loads of other multiples.
This would be fine if the base speed was the same for all drive types, but it isn’t. The base speed for a CD is 1.2Mbps, for a DVD it’s 11.1Mbps and for a Blu-ray disc it’s 36Mbps.
So with current maximums, a 52x CD transfers up to 62Mbps, a 24x DVD up to 266Mbps and a 12x Blu-ray up to 432Mbps.
The "up to" is important, as it represents the best case and speed varies across the surface of the disc. As optical drives provide constant linear velocity, more data is written per second near the outside of the disc than near its centre, so for most of the time, the transfer rate will be lower than the stated maximum.
Optical drives also come in portable forms – handy for laptop owners
Although the theoretical throughput of a USB 2.0 connection is 480Mbps, in practice several factors can lower this figure and this type of link can become a bottleneck if connecting a fast external Blu-ray drive to a device. If you are going for a very fast drive, a USB 3.0 connection is a better choice.
Bear in mind, too, that the top speed of a drive doesn’t guarantee the same speed in use unless your blank discs are also capable of that speed. A 4x DVD disc is likely to write at 4x, even in a 24x DVD drive.
These days, most DVD and Blu-ray drives are Sata devices, but if you are upgrading an older PC you may need to fit a Parallel ATA IDE device.
These are still available, but there are also inexpensive converters that plug into the back of a drive to connect a Sata device to a Pata controller or vice-versa. ®