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I was pretty close to getting Seagate's Momentus XT but have been scared off by the many problems reported on forums and feedback sites, especially in Mac Book Pros. So I'm waiting for mk 2 with some extra flash and better reliablilty I'm assuming will come out this year.

What would suit me better though is a 32+500 hybrid drive where I have more control over what is on the flash drive and what is on the disk drive. So there are 2 physical partitions within the one 2.5" hard drive enclosure which use different media internally (32GB for core files and 500GB for data and multimedia). The partitions would be locked so they can't be changed. - Or even better, the disk driver just makes them appear as two disks to the OS that share the same bus... Perhaps it's ok if the bios just sees the first drive until the OS is loaded. Is either of it technically possible? Obviously difficult to market outside of the enthusiast market.

The SSD memory modules can be pretty small right, so they could even make them a card that plugs into a secondary connection on the enclosure. That would be good for computer builders as well as for upgrading and recoverability. Then future operating systems could recognise these system SSD drives and automatically install the OS + swap files on it. While placing document libraries on the larger data drive. While in the longer term HDD will probably disapear there will always be a trade off between speed, storage size and expense.

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I'd love something like this. BTW, you might also be interested in my somewhat related SU question Out of Band Disk Partitioning and Tables? – Milind R Aug 26 '14 at 9:48
up vote 2 down vote accepted

Exposing the SSD as a separate partition would lose the biggest benefit of hybrid.

Sure, it'd be good to get a fast SSD and a high capacity rotating disk in a single slot, since many notebooks only have one, but hybrid is more than that.

Most applications install a ton of rarely used files (help files, other languages, features that you don't personally use) in the same directory as the core files which are needed frequently. The app depends on these being in the same directory as the main program, so you can't move them off a conventional SSD. But hybrid allows the same directory to contain a combination of SSD and HDD-stored files. In effect, this means the SSD only has to be somewhere around 20% of the drive capacity in order to get SSD transfer rates on 95% or more of file accesses. Unfortunately the current hybrids aren't even near 10%.

And even if the directory structure didn't prevent you from optimizing files between SSD and HDD, it's extremely unlikely that you could split out content as optimally as the disk controller, since it can maintain statistics not only per-file, but also per-cluster.

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True, and operating systems are the worst for bloat... So really just need a larger SSD cache and improved reliability, all of which will likely come in time. 4 GB is just too small, 32GB would be a huge improvement and I'd be willing to pay for that extra space. – Aaron Jan 14 '11 at 0:36
I dunno, Microsoft Office and Visual Studio both give the underlying OS serious competition for the title of most bloated. But yeah, build a hybrid with an SSD in the range of 40-60GB and a 500-750GB rotating disk and you'd basically take over the whole storage market. I know I'd buy a few, probably convince work to buy a dozen more. Cause it would clean up on 240GB SSDs in terms of both capacity and price without sacrificing speed (ok, it wouldn't quite have the write throughput of a large SSD because it wouldn't have as many channels, but it would be superior capacity*speed/$). – Ben Voigt Jan 14 '11 at 0:54

That's not how the Momentus XT works. The SSD portion acts as a kind of solid-state cache for frequently accessed blocks. Stuff you hit a lot, such as frequently used system libraries and filesystem tracking blocks, will get migrated to the SSD blocks so access is a lot faster. Since the drive is doing this on a per-block basis, you can have files in a single directory residing on SSD and magnetic media. The firmware in the drive is what selects which blocks get moved to the faster storage.

By doing this redirection on the drive itself, normal computer uses gains most of the benefits of an SSD drive without dropping the cash. Obviously, pure SSD solutions will perform better for cases where the active files are larger than 4GB (such as with some games). But splitting the two into separate drives fundamentally breaks what makes these drives nifty.

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Yeah I know the memory-should-all-be-cache concept. That's why so much more stuff is loaded now into RAM by Windows these days. I guess once it's mature it is the best approach. I just like to have direct control sometimes... – Aaron Jan 13 '11 at 23:55

I seriously hope 2011 will see some more hybrid drive options than the Seagate Momentus XT. What I also consider VERY important is some OS-level control over what gets cached on the SSD. Manual settings in addition to an automatic, adaptive caching algorithm. Like include game files/folder (you don't necessarily use them often, but still want short loading times) or exclude media files and documents, where load times don't matter.

In principle this is already possible: combining Silverstone HDD-Boost with UltimateDefrag. The latter allows you to specify which files to defrag to the outer (=faster) sectors of the HDD, the former then clones the first (=outer) parts to the SSD.

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At least one model of drive now exists that appears to meet your requirements: the WD Black² Dual Drive, which presents to the OS as two separate drives (e.g. a 120GB SSD and a 1TB HDD) but has a single 2.5" form factor with a single SATA connection.

I haven't used one myself, and unfortunately, this particular model apparently requires the installation of some kind of proprietary driver, so I probably won't end up using one in the future either. Anyhow, here are some reviews.

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