Storage devices and RAM. From top to bottom: hard drives (laptop and desktop versions), solid-state drives (the SATA2 Samsung 470 and the SATA3 OCZ Agility 3) and system memory sticks (DDR 2 laptop and desktop versions.)

(Credit: Dong Ngo/CNET)

Besides running water, digital storage is probably the second most taken-for-granted commodity. How many times have we asked ourselves where that Web page we're viewing (like this one), the movie we're watching, the song we're listening to is stored, or even how the iPhone remembers to wake us up at 7 a.m every day Not so often, if at all. As a matter of fact, the only time that we care is when it doesn't work as intended.

Believe it or not, before information can be viewed, played back, or executed, it needs to reside somewhere. For virtually anything to happen as expected in our daily life, storage is needed.

There are many types of digital storage but in the end, the most popular forms are the good old hard drives (HDDs) and new solid state drives (SSDs). These are internal storage devices that are the backbone of most if not all storage applications, ranging from external hard drives, NAS servers, to even data centers, which basically host the entirely Internet, including cloud storage services. (Memory sticks and thumb drives are just popular derivatives of solid state storage.)

And when it comes to storage, judging from many questions friends and readers send me, there are quite a few confusions among general users as to what it actually is. This is one of the main reasons why I am writing this blog.

So let's talk storage.

Storage vs. memory

It's hard and complicated to explain in detail the difference between the storage and system memory (or just "memory" or RAM) in a computer.

In a nutshell, storage is where the information (such as Word documents, photos, movie clips, programs, and so on) is stored. In a computer, the whole operating system itself, such as Windows 7 or MacOS, is also stored on the internal storage device.

Storage is nonvolatile, meaning that the information is still there when the host device (a computer, for example) is turned off and becomes ready again when the device is turned back on. It's like a book or a paper notebook that's always there, ready for you to read or write on it.

Seagate Barracuda XT 3 TB hard drive $lazy(window.GeckoVideoPlayer, CBSi.lazy.videoPlayer, function(){ loadGeckoVideoPlayer({ parentElement: 'universalVideoid50103368', flashVars:{ autoplay: 'false', adTargetType: 'Page', adPreroll: 'true', contentType: 'id', contentValue: '50103368', playlistDisplay: 'over' } },'blogXsmall')' })'

This means when a fast Core i7-based computer is equipped with a regular hard drive, the hard drive will bottleneck the machine's performance. Most of the time this gap is very large: a fast Core i 7 processor will have a subscore of 7.9, while the fastest hard drive will have a subscore of 5.9 in the Windows Experience Index. Now the best way to get the most out of a computer is to have their components offer similar level of performance. This way you know that you don't overspend on expensive parts just to have them bogged down by other slower ones.

In other words, it's better to upgrade your current Core 2 Duo or Core 2 Quad computer to an SSD than getting a new computer that supports the new Core i architecture. The latter would likely cost more than $500, not to mention the time you have to spend setting up the new computer, moving data over, and so on.

Note that while most SSDs come in the 2.5-inch design (for laptops), some of them, such as the Vertex 3, include a drive bay converter to fit in a desktop computer. You can also buy these converters separately or even get away with having the SSD hanging inside the chassis, as it has no moving parts and is very light.

In our testing, an SSD would bring the subscore of hard drive within the Windows Experience Index to 7.0 or higher. In a system that supports SATA 3 (6Gbps), an SATA 3 SSD would bring this up to even 7.8 or 7.9, which is currently the highest for Windows 7.

And in real-world usage, replacing your current computer's main hard drive with an SSD indeed makes the computer's overall performance a world of difference. The upgrade process is actually very fast, using disk cloning software such as Acronis True Image.

This is kind of change that once you've got it, you'd never want to go back.

Why you should still keep your hard drive

While SSDs are very fast, when it comes to storage, capacity is very important. With the proliferation of user-generated content, from photos to music, from home videos to recorded TV shows, it seems we never have enough storage space. This is the area where SSDs can hardly, if at all, compete with hard drives.

While for a laptop computer, 240GB might be enough, for a desktop, that can hardly hold a person's entire digital library. This is when you still want to use a hard drive as a secondary storage device to increase storage space. The good news is that most of the read-only contents don't require fast performance for playing back, and hard drives, though significantly slower than SSDs, are more than fast enough to host them.

Other network storage solutions, such as NAS servers, don't require superfast storage device, either. Mostly because their throughput performance is determined by the network connection speed, which currently caps at 1,000Mbps (around 100MBps). External hard drives also depend on the speed of the peripheral ports, and 100MBps is also currently the cap speed of USB 3.0. For this reason, most of the long-term and high-capacity storage solutions still use hard drives and will still use them for a long time.

Those of you who have just decided to upgrade the computer's main hard drive to an SSD might want to keep the old hard drive as the secondary drive in the computer, at least for backup purposes. After all, it still holds a copy of your entire system.

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