How to Buy a Hard Drive: An Essential Guide

Do you need gigabytes or performance? Laptop upgrades or a screaming new gaming PC? We walk you through what you need to know to pick the right storage solution for your PC.

Storage. Always needed, often overlooked.

Often lost in the buzz surrounding the latest DirectX 11 GPUs and hexacore CPUs is the ability to actually store and retrieve your stuff. Your applications, games, photographs, digital music and everything else lives on your hard drive. But that boring old rotating magnetic disk just doesn't seem exciting or high tech – even though the technology in a hard drive is actually pretty incredible.

One technology that has made storage a little sexier is SSDs – solid state drives based on flash memory technology. But SSDs aren't a perfect solution, as we'll see shortly. We'll cover the gamut of storage options for your OS and apps to help you better understand what storage solution is best for your needs. (Note that we're not going to talk about optical storage, which really is secondary these days.)

We'll first touch briefly on technology and jargon, then look at several different scenarios, and try to focus on what storage options might be appropriate and cost effective. But first, let's talk tech. We'll first briefly discuss hard drives, then take a quick look at SSDs.

Good Old Fashioned Hard Drives

Hard drives consist of small platters coated with magnetically sensitive material. These platters are designed to be stacked up to five high, and run at spin rates up to 15,000RPM. Some high end desktop hard drives max out at 10,000RPM, but most performance hard drives for desktop PCs run at 7,200RPM. The 15K RPM drives are mostly used in servers.

How to Buy a Hard Drive: An Essential Guide


10,000RPM. That's really fast rotational speed. It's about as fast as you can get for a desktop hard drive.

One of the key aspects of hard drives is areal density – how many bits you can cram onto a square inch. Despite the relative maturity of the technology, hard drive makers continue to improve on areal density. Seagate and Samsung have both announced hard drives that will ship in late 2011 that offer one terabyte per platter, or 625 gigabits per square inch.

Magnetic heads, mounted on arms that are moved with an electric motor called an actuator is how the data gets written to and read from the disc. Head technology is as critical as areal density, because the heads have to be extremely sensitive to read individual bits when there are 625 billion of them in a square inch of disk space.

There are several key aspects to hard drive performance: Areal density. The more bits you can cram onto a platter, the faster the drive, all other things equal. At the same spin rate, higher bit densities means that the more data is read off the drive per linear inch as it spins. Spin rate. As you spin a drive faster, more bits travel under the head, and more data read each second. Cache. Most hard drives have some DRAM cache. More cache is generally better. The highest performance hard drives have as much as 64MB of fast DRAM cache. Head technology. The robustness and responsiveness of the motors that move the head (the head actuator) determines how quickly the head can be moved to different areas of the drive. This affects random access performance.

One thing that doesn't really affect hard drive performance these days is the interface. Even 10,000RPM drives can't fully saturate a 3gbps SATA I port. Seagate has suggested that the data coming off the 64MB cache of their latest second generation SATA 6gbps drive can saturate the bust, but this would be with brief bursts at best, and with no practical effect on performance.

How to Buy a Hard Drive: An Essential Guide

Seagate was first to market with a 7,200RPM, 3TB hard drive, but your system BIOS needs to recognize it properly if you want to configure it as one large partition.

Western Digital and Seagate also make a line of "green" (low power consumption) drives. The WD GreenPower drives typically spin at 5,400RPM, while Seagate's Barracuda Green drives usually run at 5,900RPM. Note that power usage while actually under heavy load isn't that much lower, but these drives also typically offer sophisticated sleep modes which use very little power at idle. This type of technology is gradually being migrated to higher performance drives as well.

SSD Tech

Solid State Drives are still in their infancy as a technology. Products continue to evolve, and performance increases over time. This is particularly true of random write performance. First generation SSDs were hobbled by extremely slow random write times – often much slower than old fashioned rotating platters. That's changed with newer generation of controllers, better garbage collection (which reorganizes the data to minimize the number of small, empty blocks) and trim command support with modern operating systems, in which the OS tells the SSD which blocks of data are considered deleted.

The cost per bit of SSDs is much higher than hard drives, and given the limitations of the manufacturing processes, the cost per bit will remain high, albeit declining gradually. Currently, 25nm flash memory parts are pretty much the order of the day, with 20nm on the near horizon. As Anand Shimpi noted in a recent article, the costs of flash chips prevent prices from getting lower. And the cutthroat competition means products get shipped that aren't fully baked.

Still, we've been using an SSD RAID array in our primary system for both everyday use and gaming, and it would be tough to go back. The incredibly short boot times and fast application loading are seductive, and the thought of waiting for stuff to load is painful. Most users can't afford large capacity SSDs or SSD RAID arrays, so modest size drives are pretty much the rule of the day. That's one reason you see so many 120GB drives – it's right in the sweet spot for pricing.

As with hard drives, there are a number of factors that drive performance:

The type of flash. Drives using SLC (single-level cell) flash are faster than those built with MLC (multi-level cell), but lower density, so drives built with SLC flash memory are pricier. However, SLC based drives are not only higher performing, but last longer and consume less power. That's why SLC drives are often used in server applications.

The interface. Unlike rotating platter drives, newer SSDs can saturate a 3gbps interface. That's why many are moving to the newer 6gbps SATA spec.

The controller. The controller built into the drive itself is the real secret sauce. Note that legacy hard drives also have controllers, but controllers in SSDs have a far larger impact on performance. The current darling in the SSD controller space is Sandforce, with its SF-2281. But Intel controllers are pretty good. It's also worth noting that OCZ bought Indilinx, a relatively new controller company. So the controller wars will likely go on.

The firmware. The real issue with SSDs is that they're pretty new technology. What does that mean in practical term? Bugs. If you cruise various online forums, you'll find that SSDs often have oddball issues, like blue-screens, sudden loss of capacity and more.

Before you get too mired in all the details of controllers and flash memory types, remember that any good, current generation SSD will offer performance that's nothing short of amazing, if you're coming from a rotating platter drive. After using your PC with your shiny new SSD installed, you'll find yourself expecting PCs to be that responsive – and wondering why that shiny new laptop your spouse just bought seems so damned slow. Hint: it's not the CPU or memory.

How to Buy a Hard Drive: An Essential Guide

A 120GB SSD like this Patriot Wildfire is an great performance boost for a laptop up to a couple of years old and running Windows 7.

The other important consideration to weigh when thinking about SSDs is capacity. As noted, the sweet spot right now is 120GB drives, which range in price from $170 to $300 for drives built in standard, 2.5-inch form factors. Newer 240GB drives cost well north of $300 to over $500. Want a 500GB SSD? Be prepared to shell out nearly $800 or more. So consider your budget and applications before taking the expensive step to SSDs. We'll discuss some scenarios shortly.

Now that we have some basic understanding of hard drives and SSDs, let's look at a few typical user scenarios.

The Basic Office PC

This might also be called the shared living room PC. It's usually light on performance, often with integrated graphics. The applications aren't demanding, either – office apps and internet browsing are the mainstays, with some occasional digital photo or media transcoding. The entire price of the system might be under $500.

How to Buy a Hard Drive: An Essential Guide


"Green" hard drives use less power mostly by slower rotation speeds, but also offer added sleep modes to help reduce power consumption.

This is the perfect PC for one of those low power green hard drives. If you're upgrading an existing, older system, cloning the boot drive to a 1TB Western Digital GreenPower or Seagate Barracuda Green will improve responsiveness and substantially increase capacity.

The Laptop Upgrade

Your laptop is several years old, but you can't really justify refreshing the entire unit just yet. If the HDD in the laptop is 250GB or less, definitely consider replacing it with a 120GB SSD. Sure, you'll give up some capacity, but you'll gain some immediate benefits:

• Boot times will be much faster. Waiting for laptops to boot off slow, 5,400RPM 2.5-inch drives is like watching grass grow.

• You can use hibernate rather than sleep mode. Sleep consumes more power than hibernate, but a system with an SSD will come back from hibernate nearly as fast as a system waking up from sleep.

• SSDs are rugged, since there are no moving parts. So the shocks and jolts experienced by most mobile PCs will have little effect on an SSD.

How to Buy a Hard Drive: An Essential Guide

If you need capacity in a laptop, this 7,200RPM, 750GB drive from Western Digital fits the bill.

If you really need capacity in your laptop – you travel a lot with your camera, for example, and are frequently copying and editing photos – get a high capacity, 7,200RPM drive, like Western Digital's Scorpio Black 750GB drive. An interesting alternative would be Seagate's 500GB Momentus XT Hybrid, which combines a 4GB flash memory cache with a 7,200 RPM hard drive. Performance is somewhat better than a standard hard drive, though the gains aren't nearly what they would be with a true SSD.

A Digital Media Studio

You edit a lot of photos – particularly raw DSLR photos. Or you shoot video and need a fast system with lots of capacity to edit your digital movies. You need both capacity and performance, because waiting around for large media files to load is painful. But what you get depends on your budget. There's also the issue of data security – backups are critical, but we won't discuss those here.

Let's look at some possible storage configurations.

• If your budget is tight, consider a 7,200RPM, 2TB drive with 64MB of cache. These typically cost $150 or less.

• If you've got a few bucks more, build the system with a fast 1TB drive for the applications and a secondary, 2TB drive for data and scratch files.

• If your budget can spare several hundred dollars for storage, add a third, 2TB drive and combine it in a RAID 1 (that's right, RAID 1) array for data redundancy. Write performance will be a tad slower, but read performance with RAID 1 is actually a little better than a single drive.

• If you have a boatload of money, get a 240-256GB SSD as the boot drive. Use that for the apps and for the scratch files. Put all the data on a second, 2TB RAID 0 array. (You can use 3TB drives, too, but you may encounter technical issues with some motherboard BIOSes, as well as the need to configure them as GPT partitions if you're using Windows.)

Unless you're filthy rich, you won't build an all SSD digital media editing system – capacity is often king here. If you are filthy rich, it may be worth exploring dedicated hardware RAID cards and RAID 10 arrays or something similar.

Killer Gaming Rig

Games really benefit from the speed of SSDs – but games take up a vast amount of space. If all you can afford is a modest gaming system – under $1,000 – SSDs are probably out of the picture.

Or are they?

For under a hundred bucks, you can pick up a 60GB SSD. But don't use it as a boot drive. Instead, build your gaming system using a motherboard with an Intel Z68 chipset and use the small SSD as a cache for a larger (1TB or so) hard drive. (Intel brands this as "Smart Response Technology.") You'll see substantially improved storage throughput. All you need to do is first install Windows on the rotating media drive (making sure that RAID mode is enabled in the system BIOS), then add the SSD and configure it as a cache in the RAID BIOS or through Intel's software utilities.

Intel's Z68 chipset plus Smart Response adds a whole new wrinkle to modestly priced systems, and may be a bigger speed improvement with minimal cost than buying a faster CPU – though for a gaming rig, we'd choose a faster graphics card and sacrifice the SSD if we were on a really tight budget. Right now, Smart Response is only on the Z68, so AMD users or gamers running Intel X58 triple channel rigs don't have that option.

How to Buy a Hard Drive: An Essential Guide

This 250GB Intel 510 SSD is an excellent solution for a high end gaming rig, if you can afford it.

If you have a generous budget for a gaming system, a 250GB drive will handle your main apps plus a number of games; you can still add a second drive for other types of data, if you need it. And if you happen to have a lot of spare cash on hand, a second 250GB SSD in RAID 0 mode is actually more affordable than a single 500GB SSD in today's market.

Everyone's storage needs differ, but it used to be simpler: find a hard drive with the right combination of price, capacity and speed for your needs. Today, though, SSDs have upended the equation, and the right mix for your own need may be the right mix of SSD and HDD. What that combination is depends on your needs, budget and technical inclination.

How to Buy a Hard Drive: An Essential Guide

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