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Notebook hard drives square off at 7,200 RPM

A step up in performance without losing capacity
— 5:22 PM on December 2, 2010

In the world of 2.5" storage devices, solid-state drives deserve all the attention they're getting. SSDs represent a fundamental shift in storage technology, and new paradigms don't come along that often. They don't always come with this big of a step up in performance, either. Thanks to near-instantaneous access times, solid-state drives have quickly become the preferred home for a desktop PC's OS and applications. True to the roots of their 2.5" form factor, SSDs are arguably even more attractive for notebooks, which are a perfect fit for their excellent shock tolerance and snappy responsiveness.

Even though prices have fallen dramatically over the last several years, solid-state storage remains a costly proposition, at least on a cost-per-gigabyte basis. That's easy enough to work around on a desktop, where one has the luxury of installing additional hard drives. Secondary drive bays are rare in notebooks, however; you're not likely to find one outside portly gaming systems you wouldn't want on your lap.

In most notebooks, then, everything must be squeezed onto a single internal disk. If you can diet down to 120GB, you're looking at around $220 for a decent SSD. Pare your digital payload to less than 60GB, and you'll only pay around $150. Cut it to 40GB, and the price drops to around $100. Any way you slice it, some serious belt-tightening will be in order. The process is likely to be especially painful for anyone using a laptop as his primary PC.

You don't have to go the solid-state route, though. For only $10 more than the average 40GB SSD, Seagate's latest Momentus notebook drive offers a whopping 750GB at 7,200 RPM. At the same spindle speed, Samsung's Spinpoint MP4 will take you to 640GB for only $90. Hitachi and Western Digital are a little behind on capacity among 7,200-RPM notebook drives, but then you'll only pay $75 for the latest 500 Travelstar and $70 for the latest Scorpio. As appealing as solid-state drives surely are, any of those four mechanical options is a much more tenable compromise for the vast majority of notebook users.

After exploring what this quartet of hard-drive makers had to offer desktops with our 7,200-RPM terabyte round-up, I couldn't resist probing the pack's mobile offerings. Rather than focusing on a common capacity, we've taken the best 7,200-RPM model from each manufacturer's stable of notebook drives. These turbo-charged 2.5-inchers will go up against each other, of course, and they'll also face every other drive we've run through our current gauntlet of storage tests: 15 SSDs, 10 desktop drives, a handful of older notebook units, and even a mechanical/SSD crossbreed. So, without further ado, let's see how the finest 7,200-RPM notebook offerings fare.

And then there were four... more
Before exploring how the performance of these notebook drives compares to a broader range of not-so-direct competition, we should take a moment to consider how they stack up against each other. There are quite a few common elements between the drives, starting with their shared 7,200-RPM spindle speed. That's a healthy jump in rotational speed over the 5,400-RPM drives that come installed in most notebooks. On the desktop, 5,400-RPM spindle speeds are typically confined to slow, low-power models better suited to secondary mass storage than duty as system drives.

In addition to sporting the same spindle speed, all of the drives have 3Gbps Serial ATA interfaces. 6Gbps SATA is the new hotness, I know, but these notebook models won't be sustaining transfer rates that surpass the bandwidth provided by a first-gen 1.5GBps SATA link, let alone the 3Gbps one we've been using for years. The only transfers that even have a hope of pushing into 3Gbps territory are short bursts to and from the drive's DRAM cache. Incidentally, the size of that cache is another shared attribute—16MB across the board.

  Spindle speed Interface speed Cache size Areal density Total capacity Warranty length Price
Hitachi Travelstar 7K500 7,200 RPM 3Gbps 16MB 370 GB/in² 500GB Three years $75
Samsung Spinpoint MP4 7,200 RPM 3Gbps 16MB 516 GB/in² 640GB Three years $90
Seagate Momentus 750GB 7,200 RPM 3Gbps 16MB 541 GB/in² 750GB Three years $110
Scorpio Black 7,200 RPM 3Gbps 16MB 400 GB/in² 500GB Five years $70

Another similarity among these drives is the fact that they all use two platters, which seems to be the practical limit for 2.5" models aiming to slide under the 9.5-mm thickness ceiling imposed by most notebook drive bays. Despite the common platter count, we still get a range of capacities. Seagate is the only one to bring 750GB into the 7,200-RPM realm and actually have product on store shelves. Hitachi has announced a Travelstar 7K750 with similar specifications, but it's not available for sale just yet, so we're stuck with the 500GB 7K500. Western Digital's Scorpio Black line also tops out at 500GB, and that model came out later than expected, putting the company a little behind its competition. Samsung has taken an intermediate step up to 640GB.

Increasing the number of bits crammed into every square inch of platter area is key to climbing the capacity ladder. Improving this areal density has performance implications, too. Higher areal densities put more data under the drive head with each rotation, which usually leads to faster sequential transfer rates. Smaller bits do require more precise tracking, though, and that's not easy when the microscopic target is moving at the equivalent of up to 50 miles an hour.

With 375GB per platter, the Momentus obviously has the highest areal density. Samsung isn't too far behind with the Spinpoint, whose areal density is higher than one might expect from 320GB platters. The Scorpio and Travelstar both employ 250GB platters, with the Scorpio having a slight edge in data density. I'm curious to see how that pair compares in our sequential throughput tests.

Obviously, storage capacity factors into the pricing equation for all these drives. The more gigabytes you get, the more you're going to pay. We'll consider value in the context of capacity and performance a little later in the review, so there's no need to dwell too much on these sticker prices. I only mention them again because, wow, the cream of the crop for 7,200-RPM notebook drives is pretty affordable.

Even with the lowest asking price of the bunch, the Scorpio Black has an ace up its sleeve that the others can't match: five years of warranty coverage. Three-year warranties are common among mechanical hard drives, but WD kicks in a couple of years of additional coverage with its premium Black models. Seagate does something similar with its XT family, but the 750GB Momentus isn't a member.