A computer buyer’s guide: Storage devices and optical drives

Welcome to yet another episode of our computer buyer’s guide. This time we’re talking storage devices and optical disc readers.

Optical drives

An internal optical drive.
An internal optical drive.

These are a storage media that uses optical discs to store data and a laser light to read it. CDs, DVDs, and Blu rays are all optical discs: their shiny lower part contains both reflective and matte portions. When the laser hits a reflective spot, the light bounces off of it and the computer recognises it as a 1, whereas a matte spot absorbs light and returns 0 as a value. This is how practically all optical drives operate and the difference between them is in the laser technology they use. Without getting into too many technical details, a light with a shorter wavelength is able to read data stored in smaller sections of the disc, thus yielding the capacity improvement from CDs to DVDs and, a few years ago, to Blu Rays.

When you purchase an optical drive, its product description will contain three numbers followed by Xs. These refer to the speed at which the drive operates: the first is its reading speed, the second its writing speed, and the third its writing speed for rewritable discs. You may notice that Blu Ray burners have lower speeds compared to DVD burners, which in turn would appear to be slower than CD burners of yesteryear. However, that number refers to how fast a drive is times the baseline transfer speed, not the revolutions per minute, which are:

  1. Blu Ray: 4.5 MB/s;
  2. DVD: 1.39 MB/s;
  3. CD: 0.15 MB/S.

Thus, the actual speed of a 8X Blu Ray reader would be 8 x 4.5 MB/s = 36 MB/s, whereas a 52X CD reader’s is approximately 7.8 MB/s. It wouldn’t make sense for a newer technology to perform worse than its predecessor anyway.

Nowadays, optical drives are either internal or external. Internal drives slide into the case and are connected to the motherboard via a SATA data cable and to the power supply via a SATA power cable. They are, in turn, available in two varieties: regular and slimline, with two different SATA connectors. Regular drives are about 42 mm tall and are meant for use in tower computers, whereas slimline drives are meant for laptops and some mini ITX cases. Note that slimline SATA has a different connector than regular SATA and you’ll need to purchase a separate adapter for use on a desktop motherboard.

Slimline optical drives can have two different loading mechanism: tray loading, where the press of the button releases a spring that pushes the tray outward and the disk is to be secured to a cylindrical lock in the middle,  and slot-in loading, where a small motor drives the disc in place. Slot-in drives are quite rare and generally more expensive, although in my humble opinion they add a coolness factor to the computer they’re installed in.

A slot-loading optical drive.
A slot-loading optical drive.

External drives connect to your computer via USB and they make for a good investment if you need to read or write to optical media but your laptop doesn’t have one. Generally, a USB 2.0 port is sufficient to keep them fed with power and to transfer data to and from them.

We should spend a couple minutes talking about whether is worth getting an optical drive or not.

They used to be wildly popular in the ’90s and early 2000s, before the advent of broadband Internet connections, and for good reason: CDs were a huge leap forward in terms of data storage, durability, and software distribution. When the first PC CD readers appeared, 650 MB was a huge amount of data, usually even bigger than the capacity of a hard drive, and allowed software to spread quickly and easily. Starting in the 2010s, however, many computer manufacturers started phasing out optical drives from their computer. A notable brand among them was Apple, that completely eliminated optical drives from their iMacs and most of their MacBooks.

An optical drive is more of a convenience in these day than anything, but you can skip this purchase and still have a completely functional computer, especially if you purchase digitally distributed software.

Did you know? In IT, the term disc refers to optical media, whereas disk is used in relation to magnetic media.

Hard disks

A hard drive, or hard disk, is a magnetic storage device that stores operating system and user files. Inside a hard drive are a number of magnetic platters that can be read, written, or edited via a magnetic head.

An internal hard disk.
An internal hard disk.

They come in two variants: 2.5″ drives and 3.5″ drives. 2.5″ drives are smaller, require less power and are designed for use in laptops, small form factor computers, and portable USB hard drives. This enhanced portability comes at the cost of performance: it’s very common for these models to have write speeds between 40 and 50 MB/s.

3.5″ drives are bulkier, draw more power, aren’t portable, but have much better performance. These are the models to go if you’re buying a desktop computer, at least for mass storage.

So far, we’ve talked about read and write speeds, but those aren’t the only things you have to look out when you’re shopping for a hard drive. It’s also very important (if not more) to get a reliable hard drive. Storage devices are frail creatures, their platters spin all the time (unless you tweak a few settings in the operating system),  they’re susceptible to changes in heat and moisture, and as everything that has moving parts, they will eventually fail. Do your research about the RMA rates for various models of hard drives and see which ones users return for replacement less often. This won’t give you 100% certainty that your model won’t break up in a couple months, but it’s a good enough indicator.

Did you know? Despite marketing pictures showing the hard drives without the top cover, installing them as shown in those picture will result in irreversible damage to the drive, since even the tiniest speckle of powder will interfere with the magnetic head inside the disk.

Solid state drives

A solid state drive.
A solid state drive.

Solid state drives or SSDs are the latest (and greatest) thing in storage technology. When connected to your motherboard through SATA (or, in some cases, M.2), the operating system will recognise them as a normal hard drive, even using the same generic drivers, but they have no moving parts and as such are much faster than a magnetic hard drive will ever be. You can think of them USB thumb drives on steroids.

They’re so fast, that booting from an SSD will take no longer than 15 seconds, provided you have a good enough computer, and they can help breathe new life on aging hardware too. What’s not to love?

Well, for starters, they’re much more expensive than regular hard drives. When comparing the cost of two different drives, it’s useful to compare their cost per GB. Granted, this should never be the only parameter to go by when purchasing one, but price is an important factor in every purchase. The graph below shows the price per gigabyte of a the Samsung 850 EVO line of SSDs to those of the WD Blue line of HDDs. As you can see, SSDs are much more expensive than mechanical hard drives.

Comparison between the price per gigabyte of Samsung 850 EVO SSDs and WD Blue HDDs. (Click to enlarge)
Comparison between the price per gigabyte of Samsung 850 EVO SSDs and WD Blue HDDs. (Click to enlarge)

It’s already common practice for system builders to use a SSD for the operating system and programs, and a mechanical hard drive. This is likely going to remain a common practice among desktop users, at least until SSD prices start going down considerably, as shown in the graph above.

A new type of SSD takes advantage of the M.2 form factor, which uses PCI-E instead of SATA to allow for even greater transfer speeds. Unfortunately, these models are still too expensive for being used in lieu of SATA SSDs or hard drives, but it will be interesting to see how they fare once prices settle down a bit and the availability of M.2-ready motherboards becomes bigger.


In some instances, using a hard drive (even a 2.5″ one) or a SSD simply is not an option, because of budget or space constraints. This is the case with smartphones, tablets and most inexpensive 10″ or 11″ laptops. eMMC is essentially an internal USB flash drive that computer manufacturers solder directly to the motherboard for an inexpensive storage solution. In general, you should avoid computing devices with eMMCs if you have better options, lest your usage experience will be unbearably slow. As How To Geek puts it “There’s nothing wrong with eMMC in theory. Your digital camera probably doesn’t need a full solid-state drive […] Some cheap, minimal, solid-state storage in the form of eMMC works well. […] However, when you’re buying a laptop or tablet, the limitations of eMMC are more apparent.”

As said above, there are contexts where flash memory in the form of eMMC makes a whole lot of sense. But if the computer you’re buying is going to be your daily driver, you should strive to get the best performance you can get for your money. Getting a 200 € subnotebook is generally not the way to go.

How can you tell if the computer you’re interested in uses eMMC? It depends. Generally, manufacturers state the type of storage they use in the product specification page on their website. If you’re buying directly from them, you’re pretty much safe. The problem may arise when you’re buying from a large scale retail channel. If you walk in one such stores, chances are their product descriptions for inexpensive laptops will read something like “32 GB HDD” or “32 GB SSD”. No OEM has interest in purchasing SSDs of that size due to their terrible price per gigabyte ratio. Thus, you’re practically guaranteed that a computer with a memory of 32 or 64 GB uses eMMC.

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About Andrea Luciano Damico 137 Articles
Andrea Luciano Damico is a freelance translator from Italy. Among his interests are linguistics, technology, video games, and generally being a chill guy. He runs Let's Translate.it and Tech4Freelancers.net.