A few days ago we reported that Seagate would stop selling 7200 RPM 2.5” hard drives by the end of the year. Now we know why. Seagate will continue to offer 5400 RPM 2.5” drives, but if you want more performance without diving into the performance/capacity tradeoffs of an SSD Seagate will offer you its 3rd generation solid state hybrid drive (SSHD).

Once sold under the Momentus XT brand, the 3rd gen hybrid drives will simply be sold under the SSHD moniker. As Seagate alluded to many times in the past, we’ll also be getting a 3.5” hybrid drive as well. The two families will simply be called the Seagate Laptop SSHD and Seagate Desktop SSHD.

While both families will have many members, at launch we’ll see the following:

Seagate SSHD Lineup 1H 2013
  Capacity Form Factor Platters Speed NAND Price
Seagate Laptop SSHD 500GB 2.5" 7mm 1 5400 RPM 8GB MLC $79
Seagate Laptop SSHD 1TB 2.5" 9.5mm 2 5400 RPM 8GB MLC $99
Seagate Desktop SSHD 1TB 3.5" 1 7200 RPM 8GB MLC $99
Seagate Desktop SSHD 2TB 3.5" 2 7200 RPM 8GB MLC $149

All of the drives use a standard SATA interface, and all of them feature 8GB of MLC NAND (with a small portion of the NAND set aside for use in SLC mode, similar to SanDisk’s nCache). This is a disappointingly small amount of NAND, however Seagate hinted at future, higher performance versions shipping with somewhere around 32GB of NAND. As we found in our investigation of Apple’s Fusion Drive, the ideal number is likely somewhere in the 128GB - 256GB range but that puts you in a very different price class.

The benefit of using only 8GB of NAND is that Seagate is able to keep prices very low. Both Laptop and Desktop SSHDs are expected to carry around a $15 - $20 price premium over competing 7200RPM alternatives.

The NAND mostly acts as a read cache, although this time around Seagate claims it will be able to cache some writes. Seagate is understandably sensitive to writing tons of data to the NAND since it’s only an 8GB MLC device, but endurance shouldn’t be too much of a problem to navigate around with good firmware. There’s no data separation, everything that is written to NAND also exists on the hard drive - although it’s not clear if that write happens in tandem or sequentially.

Seagate is particularly proud of their very low time to use performance with the new SSHDs. Apparently Seagate aggressively tuned its algorithms to cache roughly all accesses that happen within the first minute of power on.

Although I’m not very excited about the performance of these drives compared to SSDs, their low price should make Seagate’s SSHDs an obvious choice compared to a traditional hard drive. The fact that we’ll get both 2.5” and 3.5” SSHDs is nice since many SSD users on the desktop are still consumers of mechanical drives as well. Personally I’m not sure how much I’d benefit from using Seagate’s Desktop SSHDs in my RAID array since I mostly do large block sequential transfers (which would be uncached) to/from the array. For gamers or folks who have an SSD that’s smaller than their total application footprint these SSHDs might be compelling.

When I first reviewed the Momentus XT I concluded “There's no reason for any performance oriented mechanical drive to ship without at least some small amount of NAND on board.” Three years later, it looks like that vision has finally come to be.

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  • tipoo - Tuesday, March 5, 2013 - link

    I wonder if it has write caching, and I wonder if the 750 will finally get that promised firmware update with it. How big is the flash on the 1TB laptop drive, still 8GB? Where does the performance increase come from apart from aerial density then? And is the spindle speed still 7200rpm, since they were going to stop making 7200 drives?
  • tipoo - Tuesday, March 5, 2013 - link

    Ah, drat, that's all up there. Nevermind silly old me, although i'm still curious about the first two questions, what happened to that write caching firmware they promised?
  • tipoo - Tuesday, March 5, 2013 - link

    Since the NAND is the same size and type as the one in the 750, shouldn't that be able to get a firmware update with the write caching?
  • piroroadkill - Tuesday, March 5, 2013 - link

    What's the point of making the drive slower than the old Momentus? I know they were abandoning 7200 RPM, but for their performance drive, that makes no sense.
    POSSIBLY if they added more NAND, but it's exactly the same amount as the 2nd generation Momentus XT.

    Also, anyone keeping score here notices that these drives are using MLC NAND, and the previous 2 generation Momentus XT were using SLC NAND.

    Yup, that's right, these are using no more NAND, and vastly cheaper NAND, and slower speed spindles.

    This makes absolutely no sense. Shit drives, Seagate.
  • tipoo - Tuesday, March 5, 2013 - link

    I wonder if the aerial density makes up for the spindle speed? If it's slower than the 750 I would feel better though, lol.

    Hmm, I wonder if the NAND difference from the last gen drive will prevent last gen owners from getting that write caching firmware?
  • dragosmp - Tuesday, March 5, 2013 - link

    They seem to have a lower price than the 7200RPM Momentus XT, but otherwise all the points you make are perfectly valid: slower HDD (at least in terms of access times) and lower endurance NAND.

    My 2 cents: these will show up (maybe) in cheap laptops to make them feel "just as snappy" as the more expensive ones. Otherwise a 64GB mSATA + any HDD is a faster solution and not much more expensive.
  • tipoo - Tuesday, March 5, 2013 - link

    So the SLC in the old ones would actually be even better for write caching? In that case I really do hope they update the firmware with that new functionality on the old ones, there seems to be no reason not to then other than greed.
  • dragosmp - Tuesday, March 5, 2013 - link

    It would seem more logical that if they were to activate write caching on any SSHD, it would be on the SLC based. However the controller must support it too, which it may or it may not on the old XTs (afaik). On the newer 5400RPM disks you may find a very good controller that would do better wear leveling than the XT's; although the SLC has an inherent advantage, that can be crippled by controller+firmware; the same way MLC/TLC can age pretty well as seen in Samsung's 840 series.

    I'm really not hopeful that they'd enable write caching on older XTs for many reasons: why bother if they can't monetize, no tradition in good enthusiast products and support, they're sailing on a nickel and dime market and last but not least if they'd make the old XT looking too good the new one would look even worse.

    That said I'd like that old disk updated as it had a lot of potential. For the new ones I think 32GB + 5400RPM 500GB is ideal under 100$.
  • tipoo - Tuesday, March 5, 2013 - link

    During the reviews of the 750 reviewers had access to a write caching firmware I believe, so the drive must support it. Whether they will release it is another matter.
  • Hubb1e - Tuesday, March 5, 2013 - link

    No reason other than greed? Dude, you need to rethink that word. This is a company whose purpose is to make money. There's not much business sense to upgrade old hardware with better features if you're not selling that hardware anymore. Sure, you want to keep them stable, but why spend extra cash to improve a product that is no longer on sale? That is not in the best interest of the company. That's not greed, that's business. The less money a company makes, the less people it can hire and the less products it can develop. Welcome to the real world.

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