"Fusion Drive" on a Mac Pro

Discussion in 'Mac Pro' started by bedifferent, Nov 30, 2012.

  1. macrumors 603

    bedifferent

    Joined:
    Jan 8, 2009
    Location:
    NY
    #1
    From the little I have learned on "Fusion Drive", it seems to create a single volume for a SSD and HDD, using algorithms to read/write to the respective drives in order to increase speed.

    I have a current gen (almost three years old though lol) Mac Pro with four SATA II HDD's and 1 OWC SATA III Mercery EXTREME Pro 6G ~250GB SSD. Would there be any benefit to speed, etc by creating a "Fusion Drive" system with one of my SATA bay HDD's, or is that simply a waste as it's designed for systems with limited space such as mobile systems and iMac's? Thanks!
     
  2. macrumors 6502

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    #2
    If you have a good idea of what you want out of your Mac Pro and the applications you use, you can decide how to set up your SSDs and HDDs to suit those tasks.

    When I finally replace my macpro1,1, I am seriously considering a Fusion Drive for my Aperture Library. Hopefully by that time there will be a body of research into this sort of thing. I would use an SSD for the System & Applications drive.
     
  3. macrumors 603

    VirtualRain

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    #3
    I'd rather decide what goes on my SSDs vs HDs... I don't need OS X doing that.
     
  4. macrumors 603

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    Mar 10, 2009
    #4
    If you can very accurately point at the static storage I/O bandwidth chokepoints on your workflow then Fusion isn't really going to buy you much.

    If your workflow hotspots shift around (e.g., work with a wide variety of app with associated databases and/or files ) during the course of a day then Fusion has more traction.

    If you already have a dedicated SSD for OS+Apps+home-dir and have pushed all the home-dir and large storage out seperate volumes then again ... Fusion can have limited traction.

    If 2-3 of the HDDs are highly short-stroked (i.e., using less than 50% of drive) in a RAID stripe set ( 0 , 5 ). Then Fusion has traction. Fusion will use the whole SSD generally remove about as much latency for normal sized files as "throwing away" capacity used to.
     
  5. thread starter macrumors 603

    bedifferent

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    #5
    Agreed. :)

    Thanks everyone for the points. As I have a large enough SSD for OS X/Apps/etc and 8TB (4x2TB) for my workflow(s)/Time Machine/etc, I figured "fusing" my SSD with a HDD would be rather counterproductive, but had to ask.

    The last question, my family has an iMac, last years, with a SSD and 1TB HDD. Essentially that is a fusion system, without the proper configuration. Would there be a noticeable difference in using fusion on that system? Thanks! :)
     
  6. macrumors 603

    VirtualRain

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    #6
    I guess it depends how they are managing storage... what's on what drive? What could be moved to the SSD that's not already there? Will it fit?

    I'm guessing the average home users are not going to fill an SSD unless they have a large photo library, a lot of videos, or a ton of games. In which case you have to look at how often they access stuff on the HD, the size of the files (will they fit on the SSD if Fusion were to try and move it), what's the hit loading it from the HD, what's the gain if it's moved to the SSD, and all that business.

    A use case where fusion might make sense if they have a lot of games and one week they are playing game A and then next week they are playing game B and then the following week they are back to game A... it makes sense for Fusion to move the games back and forth from the HD to the SSD for those periods.

    On the other hand, a use case where it can't or won't make sense is if they have a ton of photos or videos that they only look at occasionally. In that case, it's all best just left on the HD because moving it around is a waste of time. And, if the HD is home to a large iPhoto library for example, it might not even be movable to the SSD due to space constraints.
     
  7. macrumors member

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    Jul 21, 2011
    #7
    I wonder if it would move the entire library or only the files you actually view/open?
     
  8. macrumors 68030

    Snowy_River

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    #8
    I guess I'd draw an analogy between automatic transmission and manual transmission. While a manual transmission does give you more control, a well tuned automatic transmission is almost always more efficient.

    That being said, it's not clear, yet, how "well tuned" the Fusion control software is, at this point. However, IMO, it has the potential of being a "no-brainer" as a configuration option, if you've got the hardware for it...
     
  9. macrumors 603

    VirtualRain

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    #9
    iPhoto stores everything in a single container file, so I suspect it's all or nothing.
     
  10. hfg
    macrumors 68030

    hfg

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    Location:
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    #10
    No, Fusion functions at a much lower block level to give more granularity to the process. It will keep the frequently used parts of the container (even smaller than individual enclosed files) on the SSD.

    There are many excellent posts on how this works in these discussion threads with some links to published articles.
     
  11. macrumors 603

    VirtualRain

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    #11
    Thats cool. Is there any particular link you would recommend?
     
  12. hfg
    macrumors 68030

    hfg

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    #12
    If you search the Mac Mini, iMac, and MacBookPro forums, you will find many discussions on building Fusion drives, along with discussions on how they work. There is much confusion and mis-information regarding these, so you do have to sort through a lot of posts to find the accurate ones, but you will quickly learn to spot those.

    Here are some external links I found:

    http://arstechnica.com/apple/2012/1...ining-doc-ars-tears-open-apples-fusion-drive/

    http://www.petralli.net/2012/10/ana...macs-with-an-ssd-and-a-traditional-hard-disk/


    http://www.macworld.com/article/2015664/how-to-split-up-a-fusion-drive.html



    -howard
     
  13. macrumors 6502

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    Halifax, Canada
    #13
    No it doesn't. It stores everything in a package, which is a directory structure that appears to be a file in the Finder (but you can right-click and hit 'show package contents' to open it like any other folder).

    Additionally, as hfg said, Fusion Drive operates at the block level, so even if it was a single large file (like Outlook on Windows stores email), you'd still see some use from it.

    I built a Fusion drive in a MacBook Pro. Fairly straight forward if you have a good backup and aren't intimidated by the command line.
     
  14. macrumors 603

    VirtualRain

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    #14
    Yeah, I get it now. Thanks. :)

    How is the Fusion drive benefiting you? What kind of data is it moving around that you didn't want to manage on your own?
     
  15. hfg, Dec 1, 2012
    Last edited: Dec 1, 2012

    hfg
    macrumors 68030

    hfg

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    #15
    You would find it very time consuming to manage the data even slightly as much as Fusion does. You probably "manage" your directory tree by putting entire branches (music, video, photo, etc.) on either the SSD or the HD. Fusion does it by putting the parts you aren't frequently accessing on the HD.

    The first thing you might do is put your "Applications" directory on the SSD for speedy access. How many Application files do you have? How many do you run hourly ... daily ... monthly ... never ... but they are all there on the SSD taking up space all the time.

    One example might be a game with many levels which you have been playing for awhile. You manually would put "the game" on the SSD when you bought it, and move it to the HD when you finally completed it. Imagine if you could have only the elements of the game you were actually playing on the SSD, the completed levels would be back on the HD, and levels yet to come would also be on the HD. This would include graphics elements, sounds, playspace, etc.

    Do you put your iTunes music library on the SSD or HD? How about just the songs you are listening to frequently being on the SSD? Or the pictures of your last vacation that you are actively editing being on the SSD, while pictures of last Christmas are on the HD?

    And so forth ....
     
  16. macrumors 603

    Joined:
    Mar 10, 2009
    #16
    That is exactly the case where CoreStorege (Fusion) does work well. Those very lightly used files will hit the SDD just once while doing the restore from backup after initially creating the CoreStorage logical volume. After not being used at all in normal use they will be migrated off and probably never return ( if look at photo/video just once every blue moon ).

    Extremely narrow time range peephole optimizations are very often wrong over the long term. It is long term dynamic trends with data Fusion is going to be probably do better over the long term than humans will. There are far too many files (let alone data blocks ) in flight over an extended period for a user to accurately track them.
     
  17. macrumors 603

    VirtualRain

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    #17
    Yeah, I get what you're saying, and in theory, this all sounds good... but it really only helps when you have very limited SSD storage. If all your apps, games, and iTunes library fit on your SSD, then what?

    If Fusion was launched back when 64GB SSDs were mainstream, I'd say it's a big win. However, with 256GB SSD's now available for $160 is this really a big deal?

    I think there's a simple rule of thumb here... if you could really benefit from a Fusion drive, you should have bought a bigger SSD in the first place :p :D


    In photo editing, I keep my active library on my SSD storage, and archive stuff on HD after I'm done working on it. Even if I need to go back to an old Aperture library on the HD and re-work a photo or re-export it, I can make the call as to whether it's worth moving the library back to my SSD for the duration of the job or just leave it on the HD. It's not really a big deal. Fusion might optimize this process a little bit, but on the other hand, it might just slow me down by guessing wrong too and moving something I really wanted to keep on my SSD off to HD on it's own accord. No?
     
  18. hfg
    macrumors 68030

    hfg

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    Dec 1, 2006
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    Cedar Rapids, IA. USA
    #18
    Well ... what you say is absolutely correct, and would be the norm today except for the cost. If you can justify the cost to purchase enough SSD to totally contain your entire computing environment ... you absolutely have the best system you can get today (for your storage needs).

    I am probably not the best one to justify the fusion drive ... because I do have almost 2TB of SSD in my Mac Pro ... and I love it! :) However, that is my main working computer and I could justify the expense for it. For my other computers such as my MacBook Pro and Mac Mini, I had already updated them to SSD and Hard Disk with manual management (my MacBook Airs are already all SSD :) ), and now I have converted those to a "Fusion" configuration and am pleased with the operation. I do, however, have a larger 256GB SSD in them with a 750GB 7200rpm hard disk.

    You might have fun converting your system to a "Fusion" configuration for awhile and see if you like it. It's not permanent, and you can convert it back if you are unimpressed after trying it. Do be aware, however, that you will need to backup and restore when doing the conversion as the disks are reformatted, so although it only takes a minute to perform the conversion, it may take hours of backup/restore time (unattended) to complete the operation.


    -howard
     
  19. macrumors 6502

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    Nov 17, 2005
    Location:
    Halifax, Canada
    #19
    It's in my partner's MacBook Pro. Prior to reading about the Fusion Drive, I was planning on making a SSD system/applications disk and using the old HDD for user data. If the Fusion Drive works as advertised than some of the regularly accessed user data gets put on the SSD. So, just an experiment for now, but so far so good. She has 190GB of stuff, and a 120GB SSD and a 250GB HDD.
     
  20. macrumors member

    Joined:
    Jul 21, 2011
    #20
    Fusion doesn't guess. Also, I have a 512gb m4 ssd and its not enough.
     

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