Sign in with
Sign up | Sign in
Momentus XT 750 GB Review: A Second-Gen Hybrid Hard Drive
By ,
1. Seagate's Momentus XT Picks Up FAST Technology

From this point on, when you see the word FAST, know that we're talking about an acronym for Seagate's Flash-Assisted Storage Technology. No doubt, the decision to use FAST came from someone in technical marketing to describe certain characteristics of the company's latest-generation Momentus XT hybrid hard drive.

Buzzwords, acronyms, and marketing aside, it's pretty clear what we're talking about here today: a hard drive that employs flash memory to help augment a mechanical disk's performance without the capacity compromise or premium price tag commonly associated with SSDs.

New Momentus XT 750 GB: Benchmarked against popular HDDs and SSDs.New Momentus XT 750 GB: Benchmarked against popular HDDs and SSDs.

It's important to get that definition right. After all, even the word hybrid means so many things today, though they all typically incorporate the amalgamation of two unique elements. In the automotive world, a hybrid car employs an electric motor to offload work from the familiar combustion engine. A hybrid tablet empowers a conventionally touch-oriented device with keyboard support, creating something more akin to a notebook.

In both cases, one technology remains dominant, complemented by the inclusion of the other. In the context of Seagate's Momentus XT, we're dealing with more of a hard drive than an SSD. But how does the company decide which storage medium to use, and when?

Second-Generation Hybrid Technology

The first-generation Momentus XT boasted 500 GB of capacity and 4 GB of flash memory, which the drive used to store frequently-accessed information, referred to as hot data. Today's 750 GB model doesn't deviate from that concept. However, it does incorporate more flash, which is also higher-performance. Seagate employs smarter firmware, increases interface performance by adopting SATA 6 Gb/s, and enables Native Command Queuing (NCQ).

That's all familiar territory for us, and we have no problem isolating the benefits of each evolutionary tweak. But then the company factors in benefits tied to its FAST buzzword, and we're forced to explain in more depth before tackling the benchmarks.

According to Seagate, FAST plays a role in speeding up the boot process by as much as 3x compared to a 5400 RPM hard drive. FAST is also used to describe the improved interaction between magnetic storage, NAND flash, and the firmware. The suggestion is that data handling between the various components of previous hybrid drives varied by operating environment. Now, Seagate is claiming to offer the same experience regardless of OS or storage driver. Of course, that means the Momentus XT combines the complexities of a hard drive with the heavy dependence on firmware of an SSD. Caching, wear leveling, and performance monitoring, all have to be balanced precisely in order for this to work.

Does it? Well, that's what we're here to explore.

2. Momentus XT (ST750LX003) In Detail

Seagate's new drive family still spins at 7200 RPM. However, throughput is up. Maximum capacity increases from 500 GB to 750 GB, which is really pretty generous for a mobile platform. And, if you don't need that much capacity, there's still the first-gen 500 GB model limited to SATA 3Gb/s connectivity.

As someone with a keen interest in power consumption, it would have been interesting to consider a lower-capacity drive based on a single-platter design. However, this would chip away at the point of this product: lots of space and SSD-like performance from a single storage device.

Single-Level Cell NAND Flash

As with its predecessor, Seagate's new Momentus XT employs single-level cell (SLC) flash memory.

Of course, most of us are more familiar with multi-level cell (MLC) NAND, which is much more economical for building SSDs. However, we've seen specific products, like Intel's SSD 311, capitalize on the performance and reliability advantages of SLC flash at smaller capacities, too. The same strategy applies here: use a little bit of SLC memory to a greater effect.

Modern controllers do a great job of spreading writes out across NAND, a process referred to as wear leveling. But this is only possible when the drive's total capacity isn't consumed. When there aren't any blocks available to use for shuffling data around, though, MLC flash can wear out much faster. So, Seagate's decision to go with SLC for its cache is a smart call.

Apparently, the company saw fit to increase the cache's capacity, too. Whereas the previous model included 4 GB of SLC memory, this one sports 8 GB.

Firmware Upgrades: Boot Data-Pinning And Write Caching

The ST750LX003 sports two firmware-based improvements compared to its predecessor. First, the company says that it now permanently pins system files associated with the boot process into cache, speeding that up substantially. We can confirm that this works; Windows 7 starts up in the time we're used to seeing from popular many popular SSDs. Seagate claims that the algorithm behind this feature identifies and learns boot activity to effectively pin the right data into the flash-based cache. As a result, its effect should be felt on any operating system, including Mac OS X. A quick check with a Windows XP install confirms this. Because boot data is typically executed in the same order over and over (especially compared to user activity), the premise behind this technology makes sense.

Additionally, writes are now cached as well. Although the write speed of the flash Seagate is using is specified for 100 MB/s (reads are up to 170 MB/s), this could be helpful for speeding up random transfers, which hard drives really struggle with on their own. Unfortunately, we can't confirm the validity of this second addition. Testing a number of different benchmarks, multiple times, didn't reveal any notable performance gains.

Independence: Good For Upgrades?

The fact that the Momentus XT proffers its full feature set, regardless of operating system, means that you can install the drive into any older notebook or desktop PC with a SATA interface and not worry about compatibility. NCQ support is, of course, helpful. But the self-learning algorithms are contained within the drive and able to work with any host system. The only foreseeable concern is the Momentus XT 750 GB’s 4 KB sector size. Fortunately, Seagate employs 512-byte emulation.

3. Test Setup And Benchmarks

Our testing of Seagate’s new Momentus XT 750 GB consists of three different suites:

  1. Synthetic and storage benchmarks
  2. Power consumption and efficiency testing
  3. Real-world and boot/shutdown testing
Performance Benchmark Test System
Hardware
CPUIntel Core i5-2500K (32 nm, Sandy Bridge, D2), 4C/4T, 3.3 GHz, 4x 256 KB L2 Cache, 6 MB L3 Cache, w/ HD Graphics 3000, 95 W TDP, 3.7 GHz max. Turbo Boost
Motherboard (LGA 1155)
Gigabyte Z68X-UD3H-B3, Revision: 2.0, Chipset: Intel Z68 Express, BIOS: F3
RAM2 x 2 GB DDR3-1333, Corsair TR3X6G1600C8D
System SSDIntel X25-M G1, 80 GB, Firmware 0701, SATA 3Gb/s
ControllerIntel PCH Z68 Express SATA 6Gb/s
Power SupplySeasonic X-760 760 W, SS-760KM Active PFC F3
Benchmarks
Performance Measurementsh2benchw 3.16

PCMark 7 1.0.4
I/O PerformanceIOMeter 2006.07.27
Fileserver-Benchmark
Webserver-Benchmark
Database-Benchmark
Workstation-Benchmark
Streaming Reads
Streaming Writes
4K Random Reads
4K Random Writes
System Software & Drivers
DriverDetails
Operating SystemWindows 7 x64 Ultimate SP1
Intel Chipset Driver9.2.0.1030
Intel Rapid Storage 10.​5.​0.​1026
Real World Benchmarking Test System 
Hardware
CPUIntel Core i7-2600K (32 nm, Sandy Bridge, D2), 4C/8T, 3.4 GHz, 4x 256 KB L2 Cache, 8 MB L3 Cache, w/ HD Graphics 3000, 95 W TDP, 3.8 GHz max. Turbo Boost
Motherboard (LGA 1155)
Intel DP67BG, Chipset: Intel P67 Express, BIOS: 2040
RAM2 x 4 GB DDR3-1333, Kingston KHX1600C9D3K2/8GX
Discrete GraphicsAMD Radeon HD 6850, GPU: Barts (775 MHz), Graphics RAM: 1024 MB GDDR5 (2000 MHz), Stream Processors: 960
ControllerIntel PCH P67 Express SATA 6 Gb/s
Power SupplySeasonic X-760 760 W, SS-760KM Active PFC F3
Benchmarks
Performance MeasurementsBoot Timer
System Software & Drivers
DriverDetails
Operating SystemWindows 7 x64 Ultimate SP1
Intel Chipset Driver9.2.0.1030
Intel Rapid Storage 10.​5.​0.​1026
Drive Power Consumption Test System
Hardware
CPUIntel Core 2 Extreme X7800 (65 nm, Merom XE, E1), 2C/2T, 2.6 GHz, 4 MB L2 Cache, 44 W TDP
Motherboard (Sockek 478)MSI Fuzzy GM965, Revision: 1.0, Chipset: Intel GM965, BIOS: A9803IMS.220
RAM2x 1 GB DDR2-666, Crucial BallistiX CM128M6416U27AD2F-3VX
System HDDWestern Digital WD3200BEVT, 320 GB, SATA 3Gb/s, 5400 RPM
ControllerIntel ICH8-ME
Power SupplySeasonic X-760 760 W, SS-760KM Active PFC F3
Benchmarks
Video PlaybackVLC 1.1.1
Big_Buck_Bunny_1080p
I/O PerformanceIOMeter 2006.07.27
Database-Benchmark
Streaming Writes
System Software & Drivers
DriverDetails
Operating SystemWindows 7 x64 Ultimate SP1
Intel Chipset Driver9.2.0.1021
Intel Graphics15.12.75.4.64
4. Benchmark Results: CrystalDiskMark 4 KB And 512 KB Random Read/Write

The Momentus XT’s cache memory is designed to accelerate operations that are seen to happen repeatedly. Hence, it does not come as a surprise that the drive fails to accelerate the important 4 KB random operations.

CrystalDiskMark 4 KB Random Read/Write

512 KB Random Read/Write

5. Benchmark Results: Iometer 4 KB Random Read/Write And Application Test Patterns

Iometer 4 KB Random Read/Write

Although there are conditions under which the hybrid drives show better performance, we ran the test script for quite a while to make sure that the results reflect typical performance for true random operation.

We don't see significant performance gains here, but the new Momentus XT 750 GB is clearly faster than its predecessor.

Iometer Application Test Patterns

The three test patterns that emulate typical system (server) applications aren't any faster on the Momentus XT compared to other hard drives, since caching doesn't seem to help in the face of lots of random activity. In those workloads, you're as good or better off with other hard drive products. Better still, an SSD could give you up to 40x more performance.

Of course, these tests aren't representative of the desktop or notebook PC environments for which the Momentus XT was really designed. We wanted to run them anyway, though, to test for the effects of write caching.

6. Benchmark Results: Throughput And Streaming Performance

Streaming reads testing reveals that the new Momentus XT 750 GB is, in fact, quite a bit faster than the older 500 GB first-generation drive. However, its performance is very much like other 7200 RPM drives in the 2.5” space, so there are no surprises there.

CrystalDiskMark confirms the results we get with Iometer when testing sequential read or write performance.

7. Benchmark Results: PCMark 7

We ran PCMark 7 five times before reporting these results. The diagram at the bottom of this page shows you the overall storage performance for each of the test runs leading up to the final set.

Finally, we see performance improvements that are noticeable. The new drive clearly delivers more performance when loading applications than its 500 GB predecessor. It's also able to outpace fast desktop-class hard drives like Western Digital's VelociRaptor at 10 000 RPM.

Once again, the Momentus XT clearly delivers more performance than the other hard drives we tested. It doesn't approach the SSDs in our comparison, but it still shows admirably.

The overall PCMark 7 storage suite results demonstrate that Seagate's new Momentus XT can certainly take a step toward SSD-class performance after a number of runs. So far, so good. Let’s see if these results are mirrored in real-world metrics.

8. Benchmark Results: Windows 7 Boot/Shutdown And Application Launch

Once again, we ran the scripts in this real-world test five times before recording the final result. The idea was to replicate what you'd see after a short period of real-world use (rather than the fresh-out-of-box performance you'd only see once).

Windows 7 Boot/Shutdown Time

Pleasantly, Seagate’s Momentus XT 750 GB actually delivers a Windows 7 start-up time of 10.6 seconds on our test system, while the SSDs we included all dip in under eight seconds. That few-second gap is pretty reasonable, considering that competing mobile hard drives take almost 30 seconds to boot the same machine. It'd take a pricey 10 000 RPM disk to even come close to the first-gen Momentus XT. The new model increases performance even further.

It’s also nice to see that boot times improve as early as the second start-up. This is where the Momentus XT 750 GB is much better than its predecessor, which needed 3-5 repetitions to deliver noticeable improvements. Moreover, the overall performance of this second-gen drive is still better across all iterations than the 500 GB drive's best effort.

The performance difference shutting Windows 7 down is much less striking than the start-up results. Again, the new drives deliver respectable performance, nearly matching Western Digital's VelociRaptor.

Interestingly, you don't see any speed-up after successive shutdowns. In fact, it actually takes longer to shut down after numerous repetitions, though the differences are small.

Application Start Time

What about real-world programs installed on your hard drive? Can the Momentus XT 750 GB start some of your favorite apps quicker than competing disks? Can it be as fast as SSDs?

Windows' own caching mechanisms seem to be affecting performance here, as even the conventional hard drives deliver better performance after several iterations of our application start-up script. Our test launches Internet Explorer 8, Outlook 2010, Powerpoint 2010, and Adobe Photoshop CS5. Then, it closes all of the apps and starts over.

The graphs make it pretty clear that the Momentus XT drives (both of them) deliver a notable benefit. They both see massive speed-ups after just two iterations. Although the other drives do speed up eventually, none of them do it as quickly. Rather, it takes three or four runs of the script for Windows to cache data on the competing disks and exhibit a performance boost.

9. Power Consumption Testing

We perform our idle power testing after a few minutes of drive inactivity, but without any platform power-saving mechanisms affecting our measurements. This means that each drive gets the chance to switch into its most conservative active idle mode.

Although Seagate promises lower power consumption with its 750 GB Momentus XT, we didn't see that from the idle measurement. The company's new drive draws a fairly typical 0.8 W.

Our next benchmark measures power during our Iometer-based database workload. The result is 3.3 W of power consumption from the Momentus XT 750 GB. Although not particularly impressive, this is still in the ballpark for what we've seen from 2.5" hard drives in the past.

Even an SSD can use roughly that much power in the same workload. Memoright's 240 GB FTM Plus clocks in just .1 W less.

The video playback power consumption test shows how much power a drive requires, on average, while delivering an HD video stream.

Again, we see Seagate's Momentus XT at the upper end of our range, though it's still under 2 W.

10. Momentus XT: Best Hard Drive Ever?

We're having a hard time drawing one simple conclusion about Seagate's Momentus XT. Its hybrid nature necessitates performance evaluation across multiple runs of testing. If you try to capture the disk's behavior too early, you miss its purpose entirely. At the same time, the company claims that this drive performs similar to an SSD, which it just doesn't. 

The Momentus XT is a hard drive complemented by 8 GB of flash memory that operates as a cache. So, when you hit it with a random workload, or a sequence that isn't cached, it performs just like any other 7200 RPM hard drive. That's a worst-case scenario, though.

On the other hand, the Momentus XT can also be nearly as fast as an SSD in the right situation, too. Once it has the opportunity to learn data access patterns and pin data into flash, performance improves significantly. We found that PCMark 7 storage performance typically doubles when compared to conventional 2.5” hard drives after a few repetitions of the workload. However, the most noticeable speed-up comes from booting Windows and launching popular applications. This second-generation model learns faster than its predecessor, and it more effectively minimizes load times.

If you're copying data, then you're probably willing to wait and do something else in the background. However, launching an applications means that you're about to do some sort of work, requiring you to wait until the application becomes available. We can at least say that the Momentus XT accelerates the right sort of task, then, by cutting down on the time you spend waiting. Yes, SSDs are much faster in more situations. However, in its target segment, the Momentus XT offers a great compromise between cost, performance, and capacity.

At the same time, there is hardly any noticeable impact on power consumption. Thus, this drive probably won’t help extend the battery life of your notebook. Nor will its blend of magnetic and solid-state storage hurt power use, either, though.

In choosing between an SSD or Seagate's latest effort, we'd still go with the SSD. To it, we'd add a hard drive in the same tiered configuration you're used to seeing us recommend. But consider a mobile system where you're only able to use one 2.5" storage device. Rather than being forced to pick between the big price tag and low capacity of an SSD or the mediocre performance of a hard drive, you can get as close as possible to blending the speed of flash and capacity of magnetic disks in a single device. Is it a perfect marriage? No. But the interaction between both technologies is unquestionably better than any hybrid effort seen before.

Must you pay extra for the hybrid functionality? Compared to 5400 RPM, 750 GB, 2.5" disks, sure. Those sell for as little as $110 right now. But the Momentus XT is actually less expensive than Western Digital's Scorpio Black 750 GB, which is pretty impressive. So, in environments only able to take a single 2.5" device, the Momentus XT is a great fit.