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back to article Apple adds Fusion Drive IO to iMac

Apple's new and thinner iMac has a Fusion Drive combining flash speed and disk capacity. At a launch event today introducing a roster of new Apple products, there was an iMac refresh featuring the deletion of the optical drive and the addition of a Fusion Drive; a twin drive configuration with 128GB of flash storage and a 1TB or …

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Silver badge

So two physical drives are merged at the same mount point?

That'd require some significant rewiring within HFS+, wouldn't it? I mean it's obviously trivial to have, say, /Applications on the SSD and /users on the platter but from the announcements it sounds like they're talking about moving individual files between them but still having them appear to software to be in the same place?

Probably I'm relying on faulty information.

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Re: So two physical drives are merged at the same mount point?

I'm betting it's done in the driver rather than the filesystem -- seems like a more sensible place for that kind of chicanery, to me at least.

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Anonymous Coward

Re: So two physical drives are merged at the same mount point?

According to this picture (if that link works) it's two physical.

It appears to be an mSATA(ish) SSD (128GB up to 768GB), and a separate traditional HDD (1-3TB). It sounded like the OS is doing the caching (ReadyBoost on steroids?).

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Logical Volume Manager

"Either Apple has big plans for CoreStorage, or some Apple software engineer got way ahead of himself and designed a complete logical volume manager just to house FileVault data! "

-from an article written August 2011

http://blog.fosketts.net/2011/08/04/mac-osx-lion-corestorage-volume-manager/

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Rounded corners, prior art, &c., &c.

There, that's that sorted.

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Bronze badge

very easy to do on other hardware

I think most new intel chipsets have this functionality built in. You build your system on to the big spinning drive and then in the intel storage management you combine in the SSD, the driver takes care of the rest.

I think I'd rather have the drives separate, use the big disk for storage and the SSD for the system.

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I don't know much about hybrids, but...

Surely the problem with that is it leaves some huge OS files you never use (in particular OS X's huge language file bundles) are left on the SSD whereas photos (which really could benefit from being on an SSD) are out in the cold?

Though I'd welcome some transparent controls rather than it all being at the mercy of some algorithm somewhere, I think the automation of this system sounds a lot better.

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Re: very easy to do on other hardware

Intel's solution is to use SSD as cache; Apple appears to be talking about actually locating files on the SSD _instead of_ on the hard disk. So it's not a matter of one physical address being made faster, it's a matter of data being moved from one address range to another.

Assuming Apple's comments today were more than mere marketing puff, the system sees the two things as two drives and then manages that all for you. Analysis I've now seen elsewhere suggests that 10.7's CoreStorage acts to make a single virtual address space for all drives and the OS then shuffles the physical mapping based on whatever metrics it thinks are relevant. But the software makes two hardware things look like one rather than the one hardware thing secretly being more complicated inside.

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h3
Bronze badge

Dunno why they don't just have the SSD connected direct to the PCI-E Bus (Don't see why the abstraction is necessary for something like this. Other than less effort to design but Apple is hardly short of cash for R&D).

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Anonymous Coward

the Fusion Drive

is a £200 build-to-order 128GB/1TB option above the base £679 of the "Better" Mac mini. I do have the 4GB/500GB Seagate Momentus XT in an old MacBook, which still works great. There's no UK pricing on the 2012 iMac BTO options yet, but I notice that a £24,500 72TB RAID array is now available as a Mac mini accessory!

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Trollface

Re: the Fusion Drive

If you add the huge RAID array to a Mini, do you in essence get a Cooper Works Mini? Or maybe a Mega Mini?

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Bronze badge

Re: the Fusion Drive

Of course. The mac mini is a server.

(We need a said-with-a-straight-face icon)

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I'll bet it's not as clever as it appears

Knowing Apple, I expect it's as simple as a bodge to redirect I/O requests to the HD when they fail on the SSD, log the number of times that happens for each file in an over complicated hidden database at the root of the SSD, and anything that collects too many misses gets shifted over to the SSD.

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Silver badge

Re: I'll bet it's not as clever as it appears

They wrote their own Volume Manager, and its been in OSX for a year:

http://blog.fosketts.net/2011/08/04/mac-osx-lion-corestorage-volume-manager/

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Thumb Up

ZFS Competition ;Hierarchal Storage Management?

Author writes, "Mac OS X Mountain Lion decides which files to put in flash and which to leave on the disk drive, fusing the two drives into a single volume. The most-used applications and files are moved to the flash drive so they load quicker and receive updates faster, with reads off the flash and writes to it much faster than equivalent IOs to the disk drive."

Solaris based ZFS keeps all data on rotating rust, keeps most recently used blocks in memory, and will automatically rotate the most recently blocks (which slowly become less recently used) to flash based read cache... providing excellent performance and reliability.

Apple canceled their agreement wth Sun some years back, to ship ZFS for Apple MacOSX. This looks like a bit of hierarchal storage management, to finally compete with Solaris ZFS's flash based L2ARC!

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Silver badge

Re: ZFS Competition ;Hierarchal Storage Management?

It would seem that you are right. Apple wrote a Volume Manager called Core Storage for Lion, but until now only used it for full volume encryption though it is capable of more:

"Apple goes a step further than most volume managers, however, with the introduction of a new concept, the “logical volume family” (LVF). The LVF specifies properties that will be inherited by logical volumes that it contains. Currently, the only property specified by an LVF is FileVault encryption, but one can imagine that performance characteristics or redundancy could also be specified in this manner.

"Now two versions later, Lion includes all of the basic technology needed to effectively manage storage volumes. It is likely that the GUI simply lags behind this core technology, and we will see additional functionality added in later operating system revisions."

http://blog.fosketts.net/2011/08/04/mac-osx-lion-corestorage-volume-manager/

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Not a new concept

OCZ were doing this last year: http://www.amazon.co.uk/dp/B005J4P0JS

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Re: Not a new concept

Quite right, tiered storage has been around for years, but I think this may be the first time I've seen it on a consumer desktop.

That hybrid drive isn't tiered storage, it's a disk with a big cache, they're not the same thing.

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Flame

Love it

I love this idea an think it will really help boost performance on the iMac.

Hate to say it but Reg is right a whole load of PC manufactures will now release new products just to compete. I am sick to death of other companies playing catch up all the time on design and simple integration to apple.

Can the other companies please take 5 mins to think what can we do in terms of innovation for the home computer market.

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Anonymous Coward

Fusion drive

Think Fusion IO with go for trademark? As its very similar to their product names, Fusion ioDrive.

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I have a Seagate Momentus XT on my MBP......

It's very impressive. The caching is done on a block rather than filesystem level so is transparent to the OS and runs independently of it, I would imagine that the solution here is the same, they've just upscaled it.

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ho hum

"A flood of new PC models..."?

The Lenovo I bought for my wife two months ago has both SSD and spinny disk, transparent to Windows. Disk i/o is so much faster I drool (some would say I do that most of the time anyway).

It's not like Windows PCs were the first to use flash or SSH as a transparent caching layer either, but please watch your step as you climb off the "Apple did it first!" soapbox.

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