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What are hybrid SSD/HDD disks (like Seagate Momentus XT) practically? Do PCs recognize them as 2 separate disks (would be pretty convenient if I could really partition them independently and chose what to put on the SSD part) or what?

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up vote 4 down vote accepted

They're a HDD with a SSD as a cache. Practically speaking, they supplement the small ram cache all drives have with a significantly larger SSD cache and usually don't appear as two devices - for all intents and purposes appear as a single HDD (as opposed to say some form of ram or JBOD with a single volume).

Apparently the latest drives do the SSD caching entirely transparently. Older drives needed a driver. Neither drive seems to allow for independent use of the SSD cache.

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I don't want transparent SSD cache, I want 2 separate disks (and SSD and a HDD) in a same 2.5-inch case using a single SATA connector so that I'd be able to install them both in place of a single HDD in my laptop. Are there such models available? I'd like to put my OS, applications and some rarely-changed data files on the SSD part and keep my actively-changed/added/removed data files on the HDD part. – Ivan Jun 5 '12 at 12:13

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