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Author: stevenjklein Big funky green star, 20000 posts Feste Award Nominee! Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: of 65466  
Subject: Fusion Drive isn't caching, it's tiering Date: 11/13/2012 10:33 AM
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There's been a debate about whether or not Apple's Fusion Drive is an example of caching.

Just now I've learned that there's another term that seems to apply better: tiering.

This article (which predates Fusion Drive by a year) explains the difference: http://www.informationweek.com/storage/systems/ssd-options-t...
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Author: FlyingDiver Big gold star, 5000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 61390 of 65466
Subject: Re: Fusion Drive isn't caching, it's tiering Date: 11/13/2012 12:02 PM
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There was a long thread about that on the AAPL board. Some people insist that tiering is just an edge case of caching, and that it's still appropriate to call the Fusion Drive a caching system. I gave up trying to explain why they were wrong...

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Author: stevenjklein Big funky green star, 20000 posts Feste Award Nominee! Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 61393 of 65466
Subject: Re: Fusion Drive isn't caching, it's tiering Date: 11/13/2012 1:50 PM
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I had thought the thread was on this board, which is why I posted it here.

FWIW, I agree with you; tiering is NOT caching.

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Author: HMALETTER Big gold star, 5000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 61424 of 65466
Subject: Re: Fusion Drive isn't caching, it's tiering Date: 11/15/2012 11:32 AM
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What do you think about this point, and how does Apple address it in the Fusion drive?


"A big difference between cache and automated tiering is that the data in cache is always a second copy of the data that is on the hard drive. Automated tiering is an actual move of data from the hard drive. Failure of the cache rarely produces a data loss, just a performance loss since everything would need to be served from mechanical drives until the cache can be replaced.
Since the SSD tier holds potentially the only copy of data in an automated tiering system, the failure of the SSD tier can't be tolerated so these systems have to set the SSD tier in a redundant configuration by using a RAID-like data protection scheme. The overhead of that protection, RAID parity bit calculation for example, may impact performance and of course any RAID algorithm requires extra disk capacity. Having to purchase extra SSD to support a RAID-like function makes an already premium priced technology even more expensive."

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Author: stevenjklein Big funky green star, 20000 posts Feste Award Nominee! Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 61436 of 65466
Subject: Re: Fusion Drive isn't caching, it's tiering Date: 11/15/2012 3:12 PM
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What do you think about this point…

Context is important. The very first sentence mentions a "data center," and that's a tipoff that the article is targeted at businesses with servers.

Because the comment you highlighted is equally true of a user with a single traditional (spinning) hard drive: "The failure of the spinning drive can't be tolerated…"

For most users, the solution is to simply back up a Fusion drive just as they would back up any other hard drive.

If they need fault tolerance, then they need RAID. That's true for any kind of storage solution, whether or not it includes an SSD.

From the users perspective, a Fusion Drive is no different from a regular hard drive.

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Author: FlyingDiver Big gold star, 5000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 61441 of 65466
Subject: Re: Fusion Drive isn't caching, it's tiering Date: 11/15/2012 6:40 PM
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What do you think about this point, and how does Apple address it in the Fusion drive?

With TimeMachine. Apple sells consumer grade computers, and none of the come (out of the box) with data redundancy.

joe

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