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HDD + Flash = Seagate Momentus XT

Momentus XT Review: Seagate's Marriage Of The HDD And Flash Memory
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The hard drive component of the Momentus XT is based on Seagate's Momentus 7200 design. Therefore, you can get comparable capacities: Seagate offers 500, 320 and 250GB. Our test sample was the 500GB flagship, called the ST95005620AS. All drives are equipped with a large 32MB cache memory (don't confuse this with the flash memory). Compared to 8MB or 16MB cache on most other 2.5” drives, this is quite a step forward. 

The new drives are based on a SATA 3Gb/s interface with NCQ support, and while some people might have expected a 6 Gb/s interface, we don’t believe this is an issue at all. In the end, there has only been one 2.5” flash SSD capable of delivering enough throughput to turn SATA 3 Gb/s into a potential bottleneck. This is not the case on the Momentus XT, as throughput is limited to 193 MB/s on the interface and 109 MB/s from the physical drive.

Temperature and Power

We like the temperature specifications that allow the drive to operate between 0°C and 60°C. The power requirement is increased, most likely due to the onboard 4GB flash memory. We measured 1.3W idle power on the Momentus XT versus 1.0-1.1W on the current 7,200 RPM 2.5” hard drive competition. Power at peak throughput reaches 3.1W, which is about the same as on conventional 7,200 RPM drives; power consumption in workstation I/O is similar as well at 2.4W. However, 2.0W during full HD video playback is too much. Other 500GB 7,200 RPM drives require between 1.1W and 1.7W here. The consequences can be found in the MobileMark test results, as the battery runtime on the Momentus XT decreases quite a bit when compared to the Momentus 7200.4.

Low Level Performance

Our typical storage benchmarks include throughput and I/O testing, application performance, as well as power consumption and efficiency runs. Since this might not be enough to do justice to the flash-enabled Momentus XT, we decided to also run SYSmark 2007 Preview and MobileMark 2007; we used the latter to get an additional performance result, as well as measure the impact on battery runtime on notebooks, which might be a buying decision for some users.

We measured peak throughput of 109.6 MB/s, which doesn’t sound like a lot by itself, but it’s actually as much as a 5,400 RPM 3.5” eco-friendly drive sends across the wires. I/O performance is typically superior to the other 7,200 RPM 2.5” drives at 120-140 I/O operations per second. Application performance in PCMark Vantage is great as well, although there are some PCMark sections in which the Momentus XT doesn’t necessarily shine. Explanation of some of the performance results can be found in the technology behind Seagate’s flash memory implementation, called Adaptive Memory Technology.

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  • 19 Hide
    jsowoc , May 24, 2010 12:27 PM
    I think these hybrid drives need an all-new testing methodology that is neither like a hard drive (as you have classified it) nor a pure SSD, nor even simply the sum of the two tests.

    You mentioned that performance *might* improve if the benchmarks were rerun. Could you re-run PCMark 3 times and see if the 3rd time is any faster than the first? The idea being that the first time is simply the hard drive, and hopefully by the 3rd (or 4th time), the data ends up in the flash.
  • 18 Hide
    mavroxur , May 24, 2010 12:28 PM
    Am I the only one that's not impressed in the least?
  • 14 Hide
    cbrei10213 , May 24, 2010 1:16 PM
    Im not. I would easily shell out the money for an 80GB ssd if it also included 500G of mechanical storage. 4G is nothing. Absolutely worthless for this. Give us something real and this will be nice.
Other Comments
  • 19 Hide
    jsowoc , May 24, 2010 12:27 PM
    I think these hybrid drives need an all-new testing methodology that is neither like a hard drive (as you have classified it) nor a pure SSD, nor even simply the sum of the two tests.

    You mentioned that performance *might* improve if the benchmarks were rerun. Could you re-run PCMark 3 times and see if the 3rd time is any faster than the first? The idea being that the first time is simply the hard drive, and hopefully by the 3rd (or 4th time), the data ends up in the flash.
  • 18 Hide
    mavroxur , May 24, 2010 12:28 PM
    Am I the only one that's not impressed in the least?
  • 14 Hide
    cbrei10213 , May 24, 2010 1:16 PM
    Im not. I would easily shell out the money for an 80GB ssd if it also included 500G of mechanical storage. 4G is nothing. Absolutely worthless for this. Give us something real and this will be nice.
  • 0 Hide
    Onus , May 24, 2010 1:21 PM
    I absolutely agree with the conclusion. You look at this like a hard drive. In some things, it appears to outperform the competition, and the price is not unreasonable. For too many other things, it is no better, or even worse. I think it is promising, but as essentially "1.0" tech, it is a little underwhelming. Hopefully all it needs is a few minor tweaks.
  • -6 Hide
    nforce4max , May 24, 2010 1:23 PM
    Some what unimpressive but then again it does well enough for most uses. What they need to do is make drives with much larger caches instead of the meager sizes that are common place. 64mb cache on the high end drives is a joke ware 128mb or 256mb would make a difference ware unlike today ware much of the bandwidth is wasted before even hitting the cable. Internally typical hard drives have up to 500mbs before that is wasted by the controller due to cache misses and seek ques.
  • 6 Hide
    Ciuy , May 24, 2010 1:24 PM
    First samples are always less impressive, but i bet this hybrid tech will be the future, atleast in a small part, of the HDD market. Ssd`s are to expensive with low cap. In 2-3 months there will be great hybrid hdds for sale.
  • -7 Hide
    cknobman , May 24, 2010 1:25 PM
    Not impressive at all but what more can you expect from Seagate afterall?

    Truth is 4gb just isnt enough anymore. Although the performance numbers are ever so slightly better than current 7200 rpm hard drive the near 50 minute hit on battery life just kills the idea. Id be willing to take the battery life hit if the I/O's were higher and I could get read speeds around 140 mbs.
  • 11 Hide
    ksa-_-jed , May 24, 2010 1:27 PM
    I think is better to wait for ssd price to go down
  • 1 Hide
    sublifer , May 24, 2010 1:46 PM
    I agree, that was rather pathetic. I expected it to at least out-perform 3.5" hard drives (smaller platter + same speed 7200rpm should = faster access, reads and writes) instead we get a last gen 2.5" drive where they added 4GB flash as a buffer and poorly utilized at that, and call it a hybrid. The idea behind hybrids is to get the best of both contributors. In this case it should be capacity of hdd plus the speed of ssd. This thing wasn't anywhere near an ssd in performance and it was a sad misuse of the "hybrid" term.

    Good review though guys. Very thorough. Its clear that Seagate needs to get back to the drawing board. Perhaps start with an ssd and work on adding hdd platter storage to it instead of trying to work in the other direction.
  • 3 Hide
    matt_b , May 24, 2010 1:50 PM
    mavroxurAm I the only one that's not impressed in the least?

    Definitely not. Just looking at the benches, the "WOW!" factor just isn't there. Price considerations, I'm not even sure if I'd buy one if there were no price differences with a conventional platter-only drive. Some things were marginal, but it also took some hits. In a notebook/laptop environment, power consumption is not the department you want to see one of those hits. If there is a future to this as the alternative to SSD only drives, then the technology is far from perfected with this as an example.....
  • 3 Hide
    jrazor247 , May 24, 2010 2:19 PM
    Is this written for an alternate universe where HD tach or better benchmark utilities don't exist?
    How bout graph of throughput and seek times over drive geometry?
    More practical is if the effectiveness of their algorithm. I'd be satisfied with some junk adapter that just spans flash memory with disk space if you could ensure the OS partition is on the flash portion of geometry.
  • -4 Hide
    Pei-chen , May 24, 2010 2:20 PM
    Consider this is Seagate (famous for their rushed work); I’ll wait for WD, Hitachi, Toshiba and even Samsung.
  • 7 Hide
    aaruni123 , May 24, 2010 2:24 PM
    nah we still want cheap SSDs
  • 9 Hide
    snotling , May 24, 2010 2:29 PM
    Anandtech.com has a different set of benchmarks his conclusion is that it has the performance level of A velociraptor.
  • -4 Hide
    shin0bi272 , May 24, 2010 2:55 PM
    Should have run at least 1 SSD in the tests. Because this drive reminds me of a toyota prius... mixing old tech with new tech and delivering a POS no one but a small niche market wants. Of course they will work on this and in 2 or 3 years have a 32gb or 64gb flash section and then we will have tests where their drive out performs a combination of a velociraptor and some other SSD in drive to drive transfer. Then people will start to consider buying one of these and they will make the biggest mistake of their lives. Listen, people, you want the SSD because its faster than pretty damned much any other drive type on the planet but they are expensive. Spending money on a drive that has less nand flash memory so you can get a regular hard drive in the same package is a marketing ploy to get you to buy this device when you really want an SSD. How many of us dont have at least 1 sata 3gb hard drive laying around thats around 320-500gb? Exactly... so what's the point in buying this drive if its half and half but the worst of both?
  • 12 Hide
    Anonymous , May 24, 2010 3:06 PM
    is it me or was the benchmarking ill conceived for such a device, the speed boost will only occur once the darn thing learns from your habits, how many times were each benchmark run can we get some stats to see if on running the same benchmark a second time yields a speed boost, or maybe an nth number of times, how many times would an application need to be run before it gets cached, once cached how much better does it perform, how comes there wasn't a windows boot up time test? im pretty sure this drive would have been pre-optimized to cache windows system files

    you can't just throw a bunch of random benchmark at this thing and expect it to perform other then a standard drive. Come on now we talking about THG here, your not suppose to miss this kind of stuff.....
  • 4 Hide
    Anonymous , May 24, 2010 3:32 PM
    The standard set of benchmarks used here doesn't really reflect normal usage where this drive is supposed to shine. Some common tasks like windows startup, application start and such done repeatedly until there is no improvement in loading times would have been nice.
  • 3 Hide
    dgingeri , May 24, 2010 3:34 PM
    I have a suggestion on how they could turn this into a write cache as well as a read cache: separate logic and SLC flash storage specifically for writes. This could be half or same capacity as the read SLC cache. The writes get handed off to the drive logic for writing, enabling the OS to continue on, and the write cache continues on in the background.

    This would also allow for higher data integrity and security. Encryption could also be done through this method.

    It would drive the cost of the drive up a little, but it would still be cheaper than a SSD, and many things would perform almost as well.

    Although, I doubt anyone at Seagate would read this...
  • 1 Hide
    elel , May 24, 2010 3:44 PM
    I agree. I think you guys should give another chance and see how much repetition helps it out, especially in OS startup.
  • 5 Hide
    rkhpedersen , May 24, 2010 4:32 PM
    Maybe the test, not the drive is flawed. According to Anandtec the drive outperforms the Velociraptor by a solid margin - meaning if you don't have the money for a SSD this is the best drive available.
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