by Brian Beeler

Seagate Momentus XT Review

Hard drive manufacturers have seen the writing on the wall; embrace flash storage or suffer the consequences. Seagate is one of the few remaining hard drive manufacturers who haven’t released a line of consumer SSDs. Today though, they have come out with a cross between flash and magnetic storage known as a solid state hybrid drive (SSHD). The hybrid hard drive concept takes a standard spindle hard drive and adds flash and pattern recognizing software to boost drive performance with repetitive tasks. But will 4GB of flash memory sitting on top of a 7200RPM drive offer a big performance gain? Read the full Seagate Momentus XT review to find out. 

Update - Seagate Momentus XT 750GB Review Posted

While the hybrid hard drive idea hasn't lead to much success in the past, Seagate's Momentus XT promises to change the game by using smarter processing and algorithms this time around with a much larger 4GB SLC buffer. Seagate hasn’t come out and made any claims that it will smoke the latest SSDs but what they are pushing is a better user experience. With common recurring tasks such as booting your system, launching the same game, or opening the same program the new Momentus XT is able to offer greater speeds than even 10,000RPM hard drives.
 
They make use of the 4GB of flash with a technology called Adaptive Memory. An algorithm runs continuously on the drive to identify data patterns. Adaptive Memory then moves the most frequently accessed information to flash memory for faster recall than what is possible from the platter part of the drive. What happens is users end up tuning the drive to suit their needs. As computing patterns change, so does the cache, so it's always keeping pace with the user. The other good news is that all this action occurs on the drive itself, so the operating system doesn't matter.
 
To make things even sweeter this technology won’t cost you an arm and a leg either. The Seagate Momentus XT comes in three capacities, 250GB (ST92505610AS),  320GB (ST93205620AS) and 500GB (ST95005620AS), with retail prices of $113, $132 and $156 respectively. Our review model is the 500GB Momentus XT. 
 
 
Technical Overview
 
Seagate Momentus 500GB Specifications:
 
  • Interface: SATA 3Gb/s with NCQ
  • 2.5" 9mm body
  • 4GB SLC Flash
  • Cache: 32MB
  • Capacity: 500GB
  • >600,000 Load/Unload Cycles
  • Spindle Speed: 7200 RPM
  • Unrecoverable read errors: 1 in 10^14
  • Average idle power: 0.8W
  • Average seek power: 1.55W
  • Acoustics (Idle Volume): 2.3 bels
  • Acoustics (Seek Volume): 2.5 bels
  • Operating Shock 350G, 1000G Non-Operating
 
Aesthetics

The Seagate Momentus XT HDD/SSD hybrid drive doesn’t really look that much different than a normal hard drive. In fact, Seagate uses the same internals on the new XT that were used in the previous 7200.4. The drive has the standard Seagate drive appearance with a simple all-white label on top of a minimalistic silver cover and black metal body. When we flip it over it still keeps the same look, hiding its hybrid secrets on the inner-facing side of the circuit board. To the naked eye nothing about this drive indicates that it is unlike any other notebook drive on the market.

Build quality is good for a consumer notebook drive. Seagate rates the operating shock at 350G, meaning this drive can survive a pretty good impact like what you might experience if you drop your notebook. The PCB (printed circuit board) has all soldered components facing the drive body to shed heat and protect components from getting hit accidentally.


Disassembly

Taking the drive apart was easy after removing countless precision Phillips head screws. With the circuit board removed we finally get to see what makes this drive so special. This drive uses two controllers, one for the flash memory segment and another for the standard hard drive operations.


With the board removed on the XT and 7200.4 we also get a closer look to see the drives differences and similarities. Both drives with the circuit boards removed are identical down to the machining of the drive surface. Looking at the circuit board we can also see that both drives use the same motor driver. That is where the similarities end though.

The Momentus XT (left) has a 4GB Micron SLC NAND module packed closely to an eASIC controller for the caching part of the drive. The standard platter interface is managed by a Seagate controller which is partially obscured from a thermal pad. Finishing off the design is a larger 32MB Winbond DDR RAM cache module, up from 16MB seen in the 7200.4.

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View Larger Image

It’s impressive to think Seagate was able to convert an off-the-shelf hard drive into a hybrid HDD/SDD with just a new circuit board and software.


Benchmarks

The performance benchmarks outlined in this review can be categorized into two sections. The first is the standard IOMeter and CrystalDiskMark section which uses randomly generated data/file sequences and the second being repeatable traces. Normally most drives interact with both sets of benchmarks in the same manner, but the Seagate Momentus XT is different. In our IOMeter and CrystalDiskMark tests you will only see raw performance, which normally might translate into real world scenarios. Since the Momentus XT actively caches repeating data patterns, its full performance won’t be seen in the first half of our tests.

In our first test we see the look at the IOMeter 2MB sequential file transfer performance of the Momentus XT. Compared to the 7200.4 it only has a lead of about 3MB/s in read speed but it has a 3MB/s drop in write speed. We are including the Velociraptor in these benchmarks since Seagate made claims directly comparing the performance of the Momentus XT to 10,000RPM drives.


In our IOMeter 2MB random transfer test we see the Momentus XT slips slightly on read speed compared to the 7200.4 but has a significant gain in write speed.


Moving to smaller random transfers in IOMeter we now look at the Momentus XT’s 4K transfer performance relates to the 7200.4 and Scorpio Black (as well as the Velociraptor). The XT’s low random read speed puts it at the bottom of our list, but its write performance is still much better than the older 7200.4.


Write latency of the Momentus XT has greatly improved from the 7200.4, with speeds being improved 37%. With this increase it still falls behind the latency of the Western Digital Scorpio Black and well under the Velociraptor. Max latency was also cut in half compared to the 7200.4, dropping from 49ms to 26ms.


IOMeter server profile tests with the Momentus XT showed only minimal gains compared to the 7200.4, and it still came up short against the Scorpio Black.


The area the Seagate Momentus XT really shone was during our real-world trace playback tests. Since each test includes normal system activity that has some repeating patterns, this lets the SSD module inside the XT actually do what it was designed to do.

Most synthetic benchmarks work with such random data that it defeats or greatly limits any internal caching algorithms used by Seagate. Traces on the other hand play back the exact LBA transfers recorded on a real system, in greater than real-time speed, allowing the drive to actively cache frequently accessed data.

For the average reader looking at our reviews it might be hard to translate high transfer speeds or random 4K performance into real-world performance. In some cases we have seen drives perform exceptionally well in transfer speeds but plummet when it came to our real-world test. With our custom StorageMark 2010 traces we hope that no matter what, any reader can see how drives stack up against each other in everyday situations.

The first real-life test is our HTPC scenario. In this test we include: playing one 720P HD movie in Media Player Classic, one 480P SD movie playing in VLC, three movies downloading simultaneously through iTunes, and one 1080i HDTV stream being recorded through Windows Media Center over a 15 minute period. Higher IOps and MB/s rates with lower latency times are preferred.

In this trace we recorded 2,986MB being written to the drive and 1,924MB being read. As you can see, much of this data was able to be captured in the XT’s onboard 4GB of SLC memory and played back at a very high speed. In this benchmark the Momentus XT lived up to its claim of performing higher than a 10,000RPM hard drive (the Velociraptor). One note, the first benchmark result, before the data was fully cached, was omitted from the final result averaging. The first result gave a score of 728 I/Os, 33MB/s, and 10.95ms average latency. This score was still well above any of the previous notebook drives, showing some caching midway through the test.

Our second real-life test covers disk activity in a productivity scenario. For all intents and purposes this test shows drive performance under normal daily activity for most users. This test includes: a three hour period operating in an office productivity environment with 32-bit Vista running Outlook 2007 connected to an Exchange server, web browsing using Chrome and IE8, editing files within Office 2007, viewing PDFs in Adobe Reader, and an hour of local music playback with two hours of additional online music via Pandora.


In this trace we recorded 4,830MB being written to the drive and 2,758MB being read. As the scoring shows this, in this trace the Momentus XT wasn’t able to surpass the Velociraptor in overall speed, but it still managed to get above the Scorpio Black, and well above the 7200.4.

Since this trace is designed to capture normal performance over a longer period of time most of the caching had to take place on the fly, where it wasn’t able to record the entire trace in its 4GB of SLC storage. While running this trace we didn’t record as big of a jump in performance after the first run. Initial performance of the drive was recorded at 413 I/Os, 12.23MB/s, and 19.34ms average latency.
 

Power Consumption
 
One of the most impressive feats of the new Momentus XT is how well it manages power consumption. You would think having a 4GB SSD coupled to a spindle drive might increase power usage, but we didn’t find that to be the case. With the XT and 7200.4 sharing the same internals it was easy to make side-by-side comparisons. Below is the power consumption chart for the Momentus XT.
 
Read activity was slightly higher on the XT, drawing 3.28w over the 7200.4’s 3.06w. Write activity and random read activity were actually less, with 3.11w and 2.63w respectively on the XT and 3.19w and 2.67w on the 7200.4. Idle power consumption also saw a decent drop, measuring 0.55w on the XT and 0.89w on the 7200.4. This shows the behind the scenes action of the flash memory and caching algorithms doesn’t have a significant impact on battery life, in fact it helped reduce the power draw of the drive.
 
Warranty
 
Seagate offers the same 5-year warranty on the Momentus XT as they do on all their other spindle hard drives. Compared to solid state drives with an average warranty length of 3-years this means they put more trust in their drive and its lifespan. One of the primary reasons behind this is probably the fact Seagate used SLC NAND flash whereas most consumer SSDs use MLC NAND flash. SLC has a useful life of around 100,000 write cycles with MLC reaching its limit at 10,000 write cycles. On the flip side during average use most consumer MLC-based drives won’t be pushing as much data through each individual memory cell like the Momentus XT will as it continuously replenishes its 4GB cache stores.
 
Conclusion
 
The Seagate Momentus XT is an excellent notebook hard drive and under the right circumstances surpasses drives well out of its class. The 4GB of cache helps to significantly improve the access of common read/write patterns that a user might see in their daily routine. At its worst it still offers a significant boost in performance over its older 7200.4 brother, but at its best it outperforms even the 10,000RPM Western Digital Velociraptor desktop hard drive.
 
For the user who might load the same programs multiple times a day this drive might be a better choice than a low-capacity SSD. At $155 for a 500GB Momentus XT it is priced under even the 80GB Intel X25-M SSD which currently sells for about $200. Power users might still want to consider other options in their workhorse machines however, if speed is worthwhile at all costs and capacity is less of a concern.
 
Overall the Seagate Momentus XT makes the most sense for a anyone who just wants a noticeable increase in notebook performance, while still getting capacity without a huge jump in price. For its intended market this drive is very hard to pass up, especially considering the highest capacity model only costs $155 retail.
 
Pros
 
  • Hybrid SSD/HDD technology can beat the Velociraptor in certain circumstances
  • 500GB for $155
  • Better power consumption than older 7200.4
 
Cons
 
  • Won’t win any endurance speed tests

Bottom Line

An SSD doesn't make sense for everyone, a drive that costs more than the notebook it's in isn't practical for most users. The Seagate Momentus XT manages to crank out more performance than any other notebook hard drive on the market, while keeping prices reasonable and capacities high. If you're looking for more speed in your regular computing activities, there's no faster hard drive on the market. 

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Update 3/21/2011 - Seagate Momentus XT SD24 Firmware Update

Update 11/29/11 - Seagate Momentus XT 750GB Review Posted