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Apple Fusion Drive Isn't SSD Cache, But Is Lots Of Cash

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Fusion Drive was the surprise announcement in Tuesday's Apple (NASDAQ:AAPL) press event. It promises all the speed of a solid-state drive (SSD), with the raw storage capacity of a conventional spinning hard drive.

But what is it? Inquiring minds want to know.

source: Apple

On the one hand, it sounds like an Apple-style rebranding of the sort of SSD cache drives that the Windows world has had for a year or two (but at three times the price).

On The Other Hand, perhaps it really is, as Apple claims, "a breakthrough concept"—or at least a technology only seen before in enterprise storage arrays. Intriguing stuff...

Darcy Travlos reports:

Apple has combined the best elements of flash memory (quick processing) with hard drive[s]...to one drive.
...
While some maintain that the hybrid technology is nothing new, neither were MP3 players. Apple just popularized them.

Lucas Mearian adds:

Fusion Drive...combines the high performance of NAND flash memory with the storage capacity of a hard disk drive. ... [It] combines a massive 128GB of...flash capacity with either a 1TB or a 3TB hard disk drive, but the two media appear as a single storage volume. ... Apple claims the Fusion Drive offers performance similar to a pure solid-state drive.
...
Laptops that sport two drives -- a high-capacity hard drive and a low-capacity solid-state "cache" drive -- are already shipping [but] tend to have smaller "cache" SSDs.

A grumpy Joel Hruska calls it an overpriced bandwagon:

...with annoying predictability, [Apple] labeled it a “breakthrough storage option,” despite the fact that Nvelo and Intel have been shipping SSD cache software for well over a year. ... One major unknown is who developed the caching solution and how well it’ll compare against...Nvelo’s Dataplex and Intel’s Rapid Storage Technology [which do] an excellent job.
...
Apple’s published benchmarks, vague as they are, suggest a similar performance boost. ...we expect we’ll like them in Mac systems — or at least we would, if it wasn’t for the price...it’ll set you back $250. ...a 128GB cache drive...Crucial’s V4 is on sale for $79.

But wait! Anand Lal Shimpi says it's not a cache:

Originally I thought this might be SSD caching but after poking around...and talking to Apple I have a better understanding. ... Total volume size is the sum of both parts. ... By default the OS and all preloaded applications are physically stored on the [SSD]. ... Apple creates a 4GB write buffer on the NAND...enough to accommodate any small file random writes which could otherwise significantly bog down performance.
...
Everything else works as an OS directed pinning algorithm instead of an SSD cache. ... [It] will physically move frequently used files, data and entire applications to the [SSD] and move less frequently used items to the hard disk.
...
The concept is interesting. ... Power users will still get better performance (and reliability benefits) of going purely with solid state storage.

And Lee Hutchinson agrees:

Technical details are scarce, but...Apple's Fusion Drive...seems more like a file-level implementation of a feature [from] big enterprise disk arrays: automatic tiering [where there are] different types of storage—some slow spinning disk, some faster spinning disk, and some solid state storage. ... [They] monitor what data is being accessed the most and can automatically move that data to a faster tier of disk [and] take data that is no longer in demand...and demote it down...onto slower stuff.
...
This is almost certainly done using Apple's Core Storage logical volume manager. ... The tracking might be implemented through Core Storage attributes or through an external on-disk database like Spotlight.

John Brownlee keeps it simple, stupid:

In other words, Fusion Drive is advanced server grade technology...from huge enterprise disk arrays. Files are moved in and out of flash...depending upon your real-life usage, guaranteeing a constantly refined and fine-tuned user experience, with none of the compromises of flash.

Meanwhile, sdotbailey2 really couldn't care less if it's cached or tiered:

I'm really trying to figure out who is worse: hipsters or geeks. ... You're both annoying. Do you think the average person knows what this was or even is now? No, they don't. Stuff like this is for nerds.

Now read this:


This is OTOH: curated, fluff-free news and commentary, for people too busy to sift the gold from the sludge. Richi Jennings is an independent analyst, writer and editor. You can Google-Plus him at +richij, follow him as @richi on Twitter, pretend to be his friend at Facebook.com/richij or just use boring old email: fs@richij.com. Richi publishes a full profile and disclosure of his industry affiliations.