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I’ve seen numerous instructions on how to setup a Fusion Drive from your own SSD and HD, e.g. Can I make a DIY Fusion Drive?

Very silly question: How would a Fusion Drive built from an SSD and a Hybriddrive (take the Seagate Momentus XT 750 GB with built-in 8 GB SSD) compare to an SSD with a standard HDD when it comes to performance/power consumption/idle behavior?

Has anyone done this? Does this make any sense at all or is the "cascaded caching" (if one can call it that way) counterproductive?

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I can't see a downside as the Momentus handles the SSD portion itself, so there won't be any conflict with Fusion. But I also can't see an upside. Since Fusion uses the SSD as a kind of primary buffer, it will negate the built-in SSD buffer of the Momentus. You won't see any improvements over a traditional HDD. – user10355 Feb 4 '13 at 0:56
... perhaps other than that the Momentus XT 750 has a 7,200 rpm platter under the hood, of which there aren’t many to my knowledge, and the few which exist are more expensive than the Momentus, but without the SSD portion or don’t meet the 9.5 mm max. height requirement for internal use in the MacBook Pros optical bay. – Dr. Woo Feb 4 '13 at 2:15
I'm lost. 7200 rpm drives are quite common and have been for quite some time. I don't see how drive speed would have any affect to the stability of Fusion. But in any case, I'd say you are wasting your money to get a hybrid drive if you plan to use it exclusively for Fusion. After all, that's what Fusion does: make use of the SSD as the cache. – user10355 Feb 4 '13 at 3:05
7200 rpm 2.5 inch SATA-III HDD with capacity of 750 GB and above, and 9.5 mm height? I don’t know many... It might sound weird, but at least here in Germany, the said Momentum XT 750 Hybrid is at around EUR 90 (USD 120) by far the cheapest drive which matches those specs. – Dr. Woo Feb 4 '13 at 3:31
The height and capacity is irrelevant to what you are asking. So is actually the rotation speed. All that matters is if your system supports the drive. And it does. Fusion will link them without issue. If it's the cheapest on the market and the dimensions are within tolerance to install, I say grab it and set up Fusion. It will function like any traditional HDD in the "array." – user10355 Feb 4 '13 at 5:24

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