Final Words

For the first time since late 2008, I went back to using a machine where a hard drive was a part of my primary storage - and I didn’t hate it. Apple’s Fusion Drive is probably the best hybrid SSD/HDD solution I’ve ever used, and it didn’t take rocket science to get here. All it took was combining a good SSD controller (Samsung’s PM830), with a large amount of NAND (128GB) and some very aggressive/intelligent software (Apple’s Core Storage LVM). Fusion Drive may not be fundamentally new, but it’s certainly the right way to do hybrid storage if you’re going to do it.

It seems that Fusion Drive is really made for the user who doesn't necessarily have a ton of applications/data, but does have a reasonable sized media collection. For that user, Fusion Drive should be a reasonable approximation of a well managed SSD/HDD setup with your big media files going to the HDD and everything that you launch frequently living on the SSD. I’m always going to ask for a larger cache, but I do believe that 128GB is a good size for most client workloads and usage models today. For me in particular I’d probably need a 256GB cache for Fusion Drive to win me over, but I understand that I’m not necessarily the target market here.

The real question is whether or not it’s worth it. I’m personally a much bigger fan of going all solid state and manually segmenting your large media files onto HDD arrays, but perhaps that’s me being set in my ways (or just me being right, not sure which one). Fusion Drive doesn’t do anything to mitigate the likelihood that a hard drive will likely fail sooner than a good SSD, whereas if you go with an internal SSD and external (Thunderbolt or USB 3.0) HDD RAID array you can control your destiny a bit better. Unfortunately, in situations where Fusion Drive is a choice, you don’t often have that flexibility.

On the iMac, Apple limits your options quite a bit. You can either buy a hard drive or the Fusion Drive on the 21.5-inch model, there’s no standalone SSD option. There the choice is a no-brainer. If you’re not going to buy your own SSD and replace the internal HDD with it (or try to see if OWC’s rMBP SSD fits), then the Fusion Drive is absolutely right choice. You’re paying handsomely for the right ($250 for 128GB of NAND is very 2011), but if you’re not willing to crack open the iMac case this is really the only way to go.

For the 27-inch iMac the decision is similarly difficult. Apple does offer a standalone SSD option, but it’s for a 768GB model that will set you back $1300. All of the sudden that $250 Fusion Drive upgrade sounds a lot more reasonable.

On the Mac mini side the decision is far simpler. The Fusion Drive is only available on the $799 configuration (for $250) but so is a 256GB SSD upgrade for $300. As long as you’re ok with using an external hard drive for mass storage, here I’d go for the big standalone SSD. The usual caveat applies: this  is only true if you’re not interested in cracking open the mini yourself and using a 3rd party SSD.

To make things simpler, I made bold the options I'd choose given Apple's current lineup in the table below. Note that this is still assuming you're not going down the DIY route (if you do go down that path, buy the biggest SSD you can find and rely on some external mass storage for everything else):

Fusion Drive Options
  Mac mini (2012) 21.5-inch iMac (2012) 27-inch iMac (2012)
Base System Cost $799 $1299/$1499 $1799/$1999
1TB Fusion Drive +$250 +$250 +$250
3TB Fusion Drive - - +$400
Largest Standalone SSD 256GB
(+$300)
- 768GB
(+$1300)

I am curious to see how long of a roadmap Fusion Drive has ahead of it. Will NAND get cheap/large enough that even the iMac can move to it exclusively? Or will we end up with systems that have more than enough NAND to easily store everything but large media files for even the most demanding of power users? In less than a year Apple could double the size of the NAND used in Fusion Drive at no real change to cost. I suspect another doubling beyond that would be necessary to really make Fusion Drive a one size fits all, but then we're talking ~2 years out at this point and I don't know how static everyone's usage models will remain over that period of time. Go out even further in time, to the post-NAND era and there are some really revolutionary things that can happen to the memory hierarchy altogether...

Fusion Drive Performance & Practical Limits
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  • Constructor - Sunday, February 3, 2013 - link

    That is an utter non-issue on a Mac.

    Simply make one last Time Machine backup before the drive switch, then restore from Time Machine afterwards.

    Done.

    That's even the process when switching to a completely new Mac – in my case I once even switched machines, architectures and OS versions all in one go, from a PowerMac G5 running Leopard to an Intel iMac under Snow Leopard. Completely painless and everything was still there exactly where and as it was on the old machine, down to the last application preference and to the last document.

    You should have an up-to-date Time Machine backup at all times anyway, not least because it is so incredibly easy to maintain.

    One of the huge advantages of Fusion Drive is that I will be able to build in an additional SSD into my Late 2009 iMac, fuse it with the regular HD and then restore the Time Machine backup to the fused drives exactly and with zero changes to the directory structure, reconnecting the new copy to the Time Machine history so that every directory will retain its full backup history right back to 2008 while still auto-optimizing performance.

    That is as close to perfect as it gets.

    That they initially charge a few bucks (or Euro) for the added speed, capacity and convenience is perfectly reasonable in my view (I'll get it for free beyond the third-party SSD and some time spent on modifying it myself).
    Reply
  • name99 - Friday, January 18, 2013 - link

    " I’m personally a much bigger fan of going all solid state and manually segmenting your large media files onto HDD arrays, but perhaps that’s me being set in my ways (or just me being right, not sure which one)."

    I don't want to complain, Anand, but your criticism is dumb. Like EVERYONE, as soon as it comes to iMacs and Mac Minis, reviewers seem to lose their minds and forget that USB3 exists.
    If you want the config you want, the obvious solution is
    - buy Fusion mac
    - add USB3 SSD
    - create a symlink from ~/Documents (or whatever it is you think you really want to be on SSD) to the USB3 SSD.

    I do wish reviews spent less time on this nonsense, criticizing in a desperate attempt to find something to complain about, and spent more time on interesting technical issues. For example
    - if one creates a 3rd party fusion device via CLI, does it actually engage in this smart transfer of data between SSD and HD? I've seen different claims on the net, and it's not clear to me, if one fuses two USB devices, how the kernel would know that one is SSD and the other is HD.

    - can one boot off such a 3rd party fusion device? My instincts would be yes, because one can boot off AppleRAID devices, and this is a later generation of tech, but I've not seen this confirmed. It IS possible that, right now, the mac Mini and iMac have a special version of 10.8.2, and so certain functionalities will not be generally exposed until 10.8.3. If someone has access to an early 10.8.3 release I would, for example, like to see what happens if one takes an older mac mini, and fuses its internal HD with a USB SSD. Can we boot it? Do we get the same sort of data back-and-forth that is described here?

    - where in the kernel are the hooks that decide to move data back and forth? If, for example, I create a JBOD of an SSD plus HD (using AppleRaid) I assume I will NOT get this sort of back and forth motion, just the usual Apple hotfile motion. But is that assumption wrong?

    - how does Intel's equivalent tech work? In particular, is there actually any HW at all involved (doing what?) or is it just a Windows driver that happens to be written by Intel, and that happens to check you have a particular chipset, before it does all its driver work via the CPU?
    Reply
  • name99 - Friday, January 18, 2013 - link

    - can one boot off such a 3rd party fusion device? My instincts would be yes, because one can boot off AppleRAID devices, and this is a later generation of tech, but I've not seen this confirmed.

    To clarify this point.
    I know that 3rd party CLI-created fusion drives can boot (and we've seen a few descriptions of this in the comments). What is NOT clear to me is whether these 3rd party drives give the full fusion experience, in particular
    - writes going first to the SSD and
    - subsequent re-shuffling of data between SSD and HD to match usage patterns.
    Reply
  • gotnate - Saturday, January 19, 2013 - link

    My personal experience with a "home made" fusion setup in my 3+ year old MacBook Pro is that does seem to be the full fusion experience.

    I happen to work from home on an iMac with a 240 GB SSD and a 3 TB hard drive that I manually manage. When I first installed my 1.24 GB fusion drive (1 TB HD + 240 GB SSD) I promptly filled up 500 GB. After that, I used the MBP as my primary workstation for a week on the road. On Monday, system performance was miserable. By Wednesday, my workflow was getting pretty snappy. On Saturday, I switched back to my iMac and was surprised to find that it felt a little slower than the MBP. I have been aching to convert the iMac to fusion drive ever since.
    Reply
  • hyrule4927 - Friday, January 18, 2013 - link

    You seem to be missing a mouse in that picture on the last page . . . Reply
  • lang999 - Friday, January 18, 2013 - link

    Another apple-INVENTION i bet they pantent it and sues western digital for copying em. Reply
  • CharonPDX - Friday, January 18, 2013 - link

    "About the only difference between how I manually organize my data and how Fusion Drive does it is I put my documents and AnandTech folder on my SSD by default. I don’t do this just for performance, but more for reliability. My HDD is more likely to die than my SSD."

    So Fusion Drive is essentially a RAID-0. If the spinning drive dies, the whole thing dies. So it doesn't matter how you organize the files. With this, you just let it do its thing and make sure to keep proper backups.

    If one of my drives were to die, I'd replace it and restore from backup before doing anything else, anyway!
    Reply
  • lan8 - Friday, January 18, 2013 - link

    Under the "Putting Fusion Drive's Performance into Perspective" heading, in the sentence: "In trying to come up with a use case than spanned both drives I und a relatively simple one." I believe that odd word "und" is probably a typo of the word "found". Reply
  • mschira - Friday, January 18, 2013 - link

    Yea the biggest nuisance is the lack of 256GB SSD option - either standalone or fusioned.
    Very very disappointing, and a bog step back from the older iMacs!
    You think the they improve on their SSD choices, right?

    You can't even get a 512 GB one - which is luxurious, but maybe justifiable.

    768SSD is a pretty insane size and price,

    M.
    Reply
  • thaidrez - Saturday, January 19, 2013 - link

    Thank you Anand for this very timely and thorough review. Like many people who have a 1 or 3 fusion drive on order from Apple, this was very eye opening or confirming. The reality is that when you stress a fusion drive, it's going to show it's colors in comparison to a 100% SSD solution. I agree that 256GB would have been more appropriate for the flash portion of this fusion solution. As far as my solution, if this helps anyone contemplating this choice. I have nearly 700GB of Media (music, photos, etc) currently spread between an external HDD and a 500GB HDD internally mounted and my 240GB SSD from OWC usually has 127GB of free space on it while hosting my OSX (2011 Mini). Looking closely at that 110+/-GB of OS "stuff", 62GB User, 28GB Applications, 6.3GB Private, 6.2GB Library, 5.5GB System, and then it tapers off from there into the MB range with use at 776 and then bin at 6.2. While I won't be able to tell exactly what is going onto the fusion or not... it seems to me that a lot of bigger files like iDevice backups, old emails, big apps I never use like iMovie and most of CS will probably be moved by Core Services over to the HDD leaving a lot of space on the flash side of the fusion disk. I can imagine that a good majority of "stuff in that 110GB of data does not really get used day to day. What about my Media? Do I really want a 2012 iMac that has a HDD in it? No! But I got the 3TB fusion because I would rather take the 900$ dollars and invest into a 1TB SSD Thunderbolt solution to keep my media on. Something I can keep if I sell the iMac or put onto my MBA or MBP. So I will take my 700GB of media, put it onto my external SSD and let my system, email, downloads, and day to day stuff run off the 3TB fusion. I also have a lot of storage that I used to keep on my old mac pro that I can now move off my NAS and put back onto my fusion, knowing I won't touch it but once every few months or so. So I can't see how using a 3TB fusion would be any different than having a 768GB given my configuration and storage plan. In fact, I see the fusion with a 1TB external SSD as a superior solution. Good luck to all Reply

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