back to article Seagate's flash-disk hybrid crosses the chasm

A million units of Seagate's flash-disk hybrid drive, the Momentus XT, have shipped inside notebook computers, firmly establishing the viability of the format. The drive is a 2.5-inch, 7,200 rpm spinning disk 500GB Momentus drive, with 4GB of flash read cache inside the drive enclosure. Active files can be loaded into the …


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  1. Scott Mckenzie

    Great balance

    Great balance between cost and performance, just don't try and get one to work in a Mac! Even with the latest firmware issues, I still have freezing problems so gave up.

    1. Andrew Katz
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      MacBook Pro

      I've had one (500GB) in my MBP since about a week after I bought it around 8 or 9 months ago. It's as 15" unibody pro (the version before they introduced Thunderbolt) and it works absolutely fine, and is nice and snappy. I'm looking forward to the enhanced one coming out so I can upgrade.

      I did initially try upgrading the MBP to a WD 1TB HDD (the thick ones do fit), but it was terribly slow, so I thought I'd trade capacity for speed and got a Momentus XT, and I'm very pleased with it.

      - Andrew

  2. Andy Nugent

    Why isn't this more common?

    Seems like a really good solution in theory, is it just not beneficial in practice?

    1. James Chaldecott
      Thumb Up

      They're great

      @Andy Nugent: No idea. I got one a year or two ago for my slightly aging Dell 1525 and it perked it up no end. Boot times went from over 6 minutes (on the original 5400rpm drive) down to 1.5 - 3 minutes and everything became much more responsive.

      The variability of boot times are a good demonstration that it's not as predictable as an SSD od spinning platter (as you never know what files the firmware will have loaded into the flash) but it's a great improvement for only £10 or so over the cost of the standard Momentus.

      I like the idea of one with a bit more flash in it, though.

    2. Captain Scarlet


      It'll probably take a lot to get the right balance, cache to much and it won't be much use cache to little and you won't be benefitting from it, there is also where do they cram in the circuitry for the rest of the drive without affecting the traditional drives performance and the actual firmware itself to deal with two completly different technologies.

      I'm waiting for a 3 and a half inch drive as I think in theory this would benefit me more as I don't use more than 1/6 of my hd's contents on a regular basis.

    3. amozillo

      The performance isn't there

      Compared to late-model SSDs, there really isn't any comparison. A small flash fraction of the disk doesn't help for the enterprise segment.

      otoh a large SSD is still too expensive so I am surprised this speed/size solution hasn't been picked up more widely by HP, Dell, Sony, even Apple (maybe Seagate was trying to gouge all of them)

  3. Tony Paulazzo

    Would this work?

    OS and programs on flash part of drive, then the rest of the disk for content, rather than just using the flash as cache.

    1. Geoff Campbell Silver badge

      That's pretty much what it does, AIUI.

      The caching is quite intelligent, I'm not sure of the exact details.


      1. Sarev

        Intelligent cacheing

        This is what I'd be worried about here - until I did a bit of Googling, of course; is it intelligent in the sense of it 'knows' what filetypes tend to be read-only and which files tend to be important to performance? Or is it more based upon some sort of analysis of recent activity, etc? I'd worry that the former would be very Windows-centric and might not provide any/enough benefit on, say, Linux or Mac.

  4. JC_

    Bit Late

    The hybrid drives were a good idea, but with SSDs getting ever cheaper I can't quite see them getting popular. A 500GB XT costs more on Amazon than a 96GB Kingston SSD, for instance. 96GB is plenty of storage for the OS, applications and data of most people, with an external (or 2nd drive) used for big movie & music collections.

    The performance of the SSD will blow away the hybrid every time, but the extra capacity of the hybrid often be used.

  5. ByeLaw101

    Well they do work

    I've got a couple of Momentus XT's and they certainly do work, speed wise when loading up apps is similar to a 15k drive. There has been problems though so make sure you have the latest firmware (although I believe some problems still persist for some users).

    The SSD part is a read cache and does not enhance writing speeds as far as I know.

  6. Riscyrich
    Thumb Up

    Great drives !

    Have installed two of the 250GB drives in >3 year old laptops recently (along with a little extra RAM of course). Made them run extremely well and very fast post 3/4 reboots - after files have been used a few times it moves them onto the flash memory.

    IMHO a couple of extra GB of RAM and one of these is a very effective way of breathing a new lease of life into an old laptop.

    Just remember to disable any auto defrag software as this trashes the 4GB read cache and you have to start all over again.


  7. Anonymous Coward

    How does it work?

    I mean.. in the background.. does it transfer files transparently to the flash part of the disk?

    Or does it appear as two separate HDDs on your system and you have to manually decide whether files go on the 4GB flash part or the remaining magnetic part?

    Exactly how do files end up on the flash portion?

    1. Geoff Campbell Silver badge

      It Just Works

      The cache is built into the drive controller, so it appears as a single SATA HDD to the machine.


  8. Anonymous Coward

    Keep going...

    With Flash memory large enough, you may even be able to shutdown the spinning part when not using heavily (which is a big issue in my vintage notebook for vibration) and of course speed the things up in general, defragmenting included.

    I guess the trick is how will the storage subsystem will decide what deserves to be in the flash part, what goes in the magnetic part, or should they redirect this decision to the user, which creates the complication of one device showing up as two. Or maybe even, should the entirety of flash be used as a ginormous cache, and let the cache algorithms sort it out, except now the cache doesn't go away when you shut it down.

    I eagerly await this stuff becoming common.

  9. quartzie

    firmware issues

    The drive seems to have some annoying firmware issues Seagate has been very slow about despite a series of firmware updates.

    On many computers, this drive will cause the system to stutter intermittently, which is particularly noticeable if you watch videos. While this can be mitigated by disabling the drive's APM (thanks, quietHDD), Seagate should really be able to do something more efficient, which doesn't seem so much like a hack.

    I do like the drive's performance, although I tend to leave my PC on for extended periods of time and don't really see the "fast boot" very often. It can be very fast loading Photoshop, but part of that achievement is down to my 6 GB of RAM and Win7's preloading.

    Generally speaking, yes the performance improvement is noticeable. But there are still issues which would make me reconsider going full-ssd if I was buying again.

  10. Steven Jones

    Decent compromise

    I have one - it works. Not the same as having an SSD system disk, but it still makes the notebook a lot more responsive, especially at boot time.

  11. Geoff Campbell Silver badge
    Thumb Up

    Works really well.

    I've got a 320GB unit in my laptop, cuts boot and program load times right down.


  12. Hairy Spod

    Only good for a short while

    Although I had brief honeymoon period and although it still boots to the OS remarkably quickly, I'm suffering awful random freezing issues on my Ubuntu based laptop. So much so that my momentus is coming out next time I can set aside a few hours of fettling time.

    (yes even applying the latest firmware for the drive from the Seagate website)

  13. Anomalous Cowherd Silver badge


    4GB? Come on people. I'd pay over the odds for a 500GB disk with 32GB of flash in a heartbeat, but 4GB? Please, I wouldn't buy a 4GB memory stick these days.

  14. Alan Brown Silver badge
    Thumb Up

    4Gb is a start

    I have a raid1 pair in my desktop. It does help.

    Bigger flash would help more on laptops, but I probably wouldn't notice (Using ZFS with a 32G chunk of SSD cache dedicated to the momentus zpool)

    SSD is still ****ing expensive compared to spinning media. My solution for the moment is 8Tb of spinning media in a zpool with 128Gb of ssd cache to help out and it works well for my purposes.

  15. clanger9
    Thumb Up

    Love it!

    I have a 500GB one in an old Macbook here. Very fast and quiet - only notable downside is that it uses a bit more power than the original 80GB job, so battery life takes a hit. Boot time on OS X Lion is a few seconds...

    Seagate support is a bit haphazard, mind. When I first got the drive (with SD24 firmware), it was hopeless (never spins down, buggy sleep/resume, pauses, etc). It wasn't clear from Seagate what to do about this.

    I upgraded to SD25 firmware and it's been perfect since.

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