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

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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.

The Value Of SSDs, Hard Drives, And Hybrid Hard Drives, Compared

Of course, performance isn't the only consideration to mull when it comes time to purchase storage. So, let's pit that one attribute against capacity, cost per bit, endurance, and reliability as well.

By including 8 GB of SLC NAND with the Momentus XT, Seagate increases cost beyond what a hard drive would run on its own, though you still pay a lot less per bit than an SSD.

Armed with 750 GB of capacity, the Momentus XT delivers a lot more space than any mainstream SSD. The drive's 8 GB of SLC NAND is used to accelerate read operations. Writes only occur following read/write modifications, or when hot data is replaced with more relevant data.

SLC NAND is rated for significantly better endurance than the MLC-based NAND found in every single desktop-oriented SSD out there. So, we don't really have any concerns about longevity. Reliability is more difficult to evaluate. At least in theory, SSDs should be more reliable than mechanical hard drives. Evidence points to some SSD vendors achieving lower RMA numbers than hard drives. Conversely, though, other manufacturers weather higher RMA rates than what we've seen reported on hard disks. So, the picture changes depending on who you're talking about. The landscape is also dynamic, since SSDs evolve so quickly. As far as we know, there is no available data on the RMA rate for hybrid hard drives. However, Seagate claims an annualized failure rate (AFR) of 0.5%.

Power consumption varies considerably between each storage solution. The Samsung 830 is rated for 0.127 W typical power consumption, while Seagate says the Momentus XT is in the neighborhood of 1.1 W. Western Digital rates its Raptor X for 9.19 W. 

Our spider chart summarizes the key strengths and weaknesses of each storage solution, suggesting that hybrid hard drives yield the best all-around value. SSDs deliver the best performance, albeit with a very high cost premium at lower capacities.

Richard Hart
67 Comments Comment from the forums
  • hmp_goose
    So the turntable was two or three gens old?
    Reply
  • 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.
    Reply
  • 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.
    Reply
  • manwell999
    The probability that your hard disk or ssd is going to fail is 1:1.
    Reply
  • hunshiki
    The idea is great in my opinion, but they could include a 16gb SSD inside the drive. Or 32.
    Reply
  • 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.
    Reply
  • 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?
    Reply
  • 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.
    Reply
  • 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).
    Reply
  • 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?
    Reply