In The Lab With Seagate's Momentus XT 750 GB Hybrid HDD

More than two years after reviewing Seagate's first-generation Momentus XT, we're back in the lab with a 750 GB model armed with 8 GB of SLC NAND and a SATA 6Gb/s interface. How does it compare to pure solid-state and hard drive technologies? We dig deep.

We've seen hard disk drive technology make significant advances over the many years we've been covering it. If you were to map out, over time, the cost of mechanical storage per gigabyte, hard drives look pretty darned good. The rate at which performance has increased isn't nearly as impressive, though. Hard drives have increasingly become performance bottlenecks in high-performance PCs. 

So, when solid-state drives first appeared on the enthusiast radar roughly three years ago, they were quickly embraced as the best single performance upgrade you could buy. An SSD's main advantage is its low access times, which are an order of magnitude faster than hard drives. That advantage, however, hasn't changed much since solid-state technology first hit the scene. Although subsequent generations of SSDs improve storage performance in other ways, there's no way to match the bang for your buck that those first SSDs offered. If you already own an SSD, you're probably better off upgrading some other component inside your PC before spending more money on a more modern solid-state drive.

Evolution in SSD technology has been primarily confined to changes in NAND and controller technology. The constant efforts to improve NAND technology have been relentless, with die shrinks occurring every year. Each time a manufacturer achieves smaller process geometry, it can push down the cost of flash memory and enable more affordable SSDs.

Even today, though, a 500 GB SSD still costs more than a well-optioned laptop. We'll never see cost parity per bit between hard drives and SSDs due to the investment that goes into such aggressive manufacturing roadmaps. SanDisk predicts that current NAND technology will continue to dominate for the rest of the decade. But plans to replace NAND with 3D ReRAM are already in progress, and newer technologies could be in production within five years. Resistive RAM will enable lower costs, better endurance, and faster random performance. So, it’s unlikely that SSDs as they exist right now will persist beyond the end of the decade.

Bottom line: SSDs are expected to remain a premium technology until they're eventually phased out. They'll never match the cost per gigabyte of hard drives, and they'll never catch the growing capacities of hard drives. Very low access times make SSDs ideal for installing an operating system and performance-sensitive applications. But their high cost makes them unsuitable for user data, like music and movie libraries.

Consequently, hard drives are typically still used for those sorts of files, resulting in a tiered storage environment. But what if you could merge both technologies into one product and achieve the best qualities of both hard drives and SSDs? Enter the hybrid hard disk drive (HHDD), a relatively new idea in the storage world. We reviewed our first hybrid hard drive more than two years ago in our Momentus XT Review: Seagate's Marriage Of The HDD And Flash Memory. This time around, we're spending some lab time with that model's successor, the 750 GB Momentus XT, comparing it to solid-state and hard disk drives.

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  • hmp_goose
    So the turntable was two or three gens old?
  • sunsmasher
    So it sounds like the hot setup is SSD for OS/Apps, and HHDD for storage of frequently used media, with a 2TB+ hard drive for storage/archiving of other media.
  • americanbrian
    I don't like your spider graph for reliability.... Does the Hybrid Drive still "work" when either the flash or spinning discs fail?

    If not (which it is easy to argue it would at least not be working properly if at all). Then you must say it has twice the chance at failure. This is because if there is a 1:1000 chance of the HD part failing, and a 1:1000 cahnce of the flash failing (your spider shows them to be roughly equal) then there is a 2:1000 chance of "drive" failure in total (or 1:500).

    That is called "probability" it is funny like that. Think of it like a weird RAID 0 array.
  • manwell999
    The probability that your hard disk or ssd is going to fail is 1:1.
  • hunshiki
    The idea is great in my opinion, but they could include a 16gb SSD inside the drive. Or 32.
  • akamrcrack
    Would have been nice to see you include SSD caching drives like the Crucial Adrenaline in this study.

    My Adrenaline + Samsung Spinpoint F3 1TB 7200rpm HDD say they are the better buys :)

    Installed my OS onto my HDD (was originally on a Crucial M4 64GB) then installed the Caching software from Dataplex and watched the sparks fly!

    Now my Spinpoint runs as fast as my Intel 320 series 120GB SSD in CrystalDiskMark :)

    Plus I can always upgrade to a 2TB HDD meaning I can have 2TB of space running at SSD speeds all day :)

    When you are a srs gamer like me and you have hundreds of games to store and no SSD capable of holding them, you begin to want to find solutions to solve that. Well ever since I installed the caching drive + software (very simple) everything about my HDD is fast!

    Momentus is old and tried. The only thing I know of that can match the performance of my HDD+SSD cache is a new gen velociraptor 1TB HDD that costs around $320. Which could get me 2TB of storage and the SSD cache and still have money left over lol so neither new gen raptors or momentus are worth the cost unless you are limited to 1x 3.5" bay in your computer.. Even then a 2.5" SSD is very easy to hide in a case..

    I've seen the argument "why not just get a regular SSD instead of the Adrenaline, won't they do the same thing?"

    My response to that is, for the average user that wants simplicity getting a SSD premade for caching that comes with quality software is the way to go. The Dataplex software is very very light and as simple as install then forget it existed.
  • A comparison with Intel's SRT technology (combines up to 64GB SSD with a traditional HD) would have been interesting. I wonder what evidence made Intel choose 64GB and Seagate choose 8GB? What is the optimal amount of SSD to pair with an HD generally speaking?
  • mariusmotea
    To test a Hybrid drive you need to use it several hours. of course that benchmarks files has been cached into the SSD. Let's see the startul speed after i browse the internet for few hours and play a game for 30 minutes. I don't belive that the statup files will be in ssd anymore.
  • dthx
    Of course a SSD + big 3.5 drive is always a better solution but... impossible to achieve in most portable PC's. This is where the hybrid shines: you don't have to choose between decent performances and sufficient and affordable capacity. I've put such a drive (and Win7 instead of Vista) in a 4 year old XPS-1330 and after a few reboots it has become an extremely capable machine (faster than any brand new laptop with a conventional HDD).
  • cscott_it
    I recall another site (maybe Anandtech?) putting a couple of these in a RAID 0 configuration and the performance scaled rather nicely. Any chance you guys are thinking about doing something like that?
  • SinisterSalad
    I've had a few of the 500GB versions. Nice to see the improved capacities. The 4GB SSD on mine was enough until BF3 with their large maps came about. I've since gone to SSD on my primary machine, but I still like and recommend these drives.
  • cknobman
    I have issues with the fact that you benchmark the $150 Momentus against a sub $100 64GB SSD. It is very well known that 64GB SSD drives perform noticeably slower than larger SSD due to fewer channels. This review should have included at least 120GB SSD especially since they can be purchased for <$110.

    Also it is noted how well the Momentus performs after several runs of a game loading or booting the OS as it recognizes the pattern and keeps the data on a SSD. I would like to see if there is a huge performance impact of something like: 3 boots to get the OS on the cache, then 3 loads of a game, then reboot the computer. Does the reboot after the multiple run of the game load to put it on the cache take forever because there was not enough cache to accommodate all the OS and the game?
  • willard
    americanbrianThat is called "probability" it is funny like that.

    You might want to take a statistics class, because that's not how probability works.
  • willard
    manwell999The probability that your hard disk or ssd is going to fail is 1:1.

    Indeed. It's pretty useless to talk about failure rates without giving a time frame. Over a long enough time, everything must eventually fail.

    Entropy must increase.
  • Sakkura
    When it comes to comparing AS SSD benchmark results, the Momentus XT and Raptor X are an order of magnitude slower than Samsung’s 830, based on access time and 4 KiB performance results.

    Looks more like roughly TWO orders of magnitude, since performance seems to range from ~20x to ~200x.
  • willard
    akamrcrackNow my Spinpoint runs as fast as my Intel 320 series 120GB SSD in CrystalDiskMark Plus I can always upgrade to a 2TB HDD meaning I can have 2TB of space running at SSD speeds all day

    No you can't. You will never have 2TB of storage running at the speed of an SSD. Your SSD can only cache as much as the SSD can hold, and you don't get the full performance of an SSD with a cache drive anyway.

    Caches perform very well when there is a small amount of data that needs to be cached, but your example of "hundreds of games" is well beyond the capabilities of a cache drive.
  • willard
    SakkuraLooks more like roughly TWO orders of magnitude, since performance seems to range from ~20x to ~200x.

    20x to 200x is one order of magnitude. Two orders would be 20x to 2,000x.
  • Sakkura
    willardYou might want to take a statistics class, because that's not how probability works.

    When you're dealing with an either/or scenario, probabilities are actually additive; P (drive 1 or 2 failing) + P (drive 1 and 2 failing) = P (drive 1 failing) + P (drive 2 failing). Having two (or more) components that can each fail makes an overall failure more likely, assuming each component is just as error-prone as otherwise. The same thing affects RAID arrays, where adding drives increases the risk of a failure, unless compensated for with redundancy (redundancy can, however, increase reliability beyond that of a single drive too). A hybrid SSD/HDD drive is similar to a RAID0 array with 2 drives in regard to failure rates; if either drive fails, you're in trouble.
  • chesteracorgi
    Mr. Hart, a fairer comparison against the Momentus would be one of the caching drives from Corsair (Accellerator) or OCZ (Synapse) using Dataplex software, combined with a HDD. Now, it may not be exactly fair even then because the caching drives have more capacity than the Momentus: but the comparison is closer or apples to apples rather than apples to oranges. But bot the technology involved and cost make thie caching SSD/HDD combination relatively even.
  • Sakkura
    willard20x to 200x is one order of magnitude. Two orders would be 20x to 2,000x.

    What I meant was that the SSD outperforms the other drives by factors of around 20 to 200 on the indicated parameters. That's about 1.3 to 2.3 orders of magnitude.
  • Tedders
    So basically, it literally is a blend of both worlds good and bad. But the more you use this HHDD the better it performs as it learns over time what you use the most? SO right now, if it were in my rig it would load Max Payne 3 really really fast as I have playing the crap out of it. Am I correct?
  • willard
    SakkuraWhen you're dealing with an either/or scenario, probabilities are actually additive

    No they aren't, you can only add probabilities when they are mutually exclusive. For example, the chance of getting Heads or Tails when flipping a coin is 100% (50% + 50%). However, the chance of getting a Heads after two flips is not 100%, because you can't add the probabilities.

    Similarly, the probability of failure of something is not the sum of the probability of failure of each of its components. Consider a hypothetical piece of equipment with five components, each of which has a 20% failure rate over a period of one week.

    After one week, there is not a 100% chance that the equipment has failed. It is very likely that it has, but the probability is not 100%, or even very close to that. There is about a 33% chance that the equipment is still functioning after that week. If we're considering failures to be random events (as the average HDD failure is), there is still a 33% chance that the equipment still works after another week, given that it survived the first week.
  • willard
    SakkuraWhat I meant was that the SSD outperforms the other drives by factors of around 20 to 200 on the indicated parameters. That's about 1.3 to 2.3 orders of magnitude.

    Ahh, I stand corrected then.
  • Farrwalker
    With the relatively low price of 4GB 240-Pin SDRAM DDR3 1600 four sticks can be had for under $100. With a system that has 16GB of RAM, is it possible for software to accomplice what a hybrid hard drive does?

    Assuming that a system has 16GB of RAM and a 1TB hard drive, is there software to use the RAM in the motherboard as a hybrid uses the flash memory contained with in the hybrid drive to increase read and writes?