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Which is the better upgrade: RAM or a fusion drive?

1583 Views 12 Replies Latest reply: Dec 12, 2012 3:28 PM by Jeff Nitschke RSS
Cameron Paterson Level 1 Level 1 (45 points)
Currently Being Moderated
Dec 11, 2012 1:08 PM

I am on the verge of ordering one of the new iMac models but I find myself in right ole quandary regarding the Fusion Drive. On the one hand it looks like interesting technology and I'm sufficiently geekly to be motivated by that. On the other hand, I am very reluctant to spend £350 for a speed bump of a second or two here and there.  (Yes, it is £350: £200 for the drive, plus £150 extra for the upper end 21.5"). A RAM upgrade seemed a much more sensible option, espeically since this cannot be upgraded later (boo hiss to that!). But then I started thinking: all-flash systems like the MacBook Air have no distinct RAM as such: it's 128 or 256Gb of flash and that's it. So what function does RAM have on a fusion drive system?? Would I not get the same benefits from a fusion drive as I would from a RAM upgrade??

Informed input much appreciated: I am very confused!

iMac, OS X Mountain Lion, 8GB RAM
  • BDAqua Level 10 Level 10 (114,805 points)

    Hi, personally I think RAM, but depends highly on what you do, RAM will be faster if needed, fusion drive makes Disk operations, like VM much faster, but with enough RAM you'll need far less VM & the Fusion speed will mostly just affect laoading & saving.

  • MartinR Level 6 Level 6 (14,560 points)

    Hello Cameron,


    RAM and the Fusion Drive are two completely different things.


    The Fusion Drive is a combination of flash storage + a hard drive in a single unit ... it is not RAM.  The flash storage in the Fusion Drive is more like a big buffer with the ability to retain data when turned off, like a hard drive can.  It's storage.


    RAM (aka memory) is what the system uses to operate when running.  It is not storage.


    IMHO you will be better off right now investing in more RAM, since it's nearly impossible to add more RAM later on (it takes and entire disassembly of the iMac to change the RAM, and probably voids the warranty).

  • crh24 Level 3 Level 3 (920 points)

    Cameron Paterson wrote:


    I see what you mean Martin. They do seem distinct but there is some overlap, isn't there? There is no RAM in a MacBook Air is there? Just a quantity of flash memory....


    Most computers today do not have RAM which is just Random Access Memory, they have Dynamic Random Access Memory or DRAM, but the 'idea' is the same.  DRAM is memory used by the OS and applications for storing objects they are working on in the computers 'memory'.


    SSD or flash is flash memory configured to handle 'hard drive' functions.  Compared to hardware disk drives with their inertia latency issues SSD is lightning quick.  The hard drive function is usually referred to as 'storage' and not as 'memory'.


    For example, my mid-2011 MacBook Air has 256GB of SSD which is flash memory used as the main disk drive.  It is very fast.  It also has 8GB of DRAM, which is enough for most applications to have room to run without paging to the SSD.  Since paging to SSD is very quick apps that have to page to the SSD run very quickly too.


    A fusion drive is one that has a SSD drive 'married' to a hardware drive via software.  Apple's implementation has a 128GB SSD and a 1TB or 3TB hard drive.  The software is designed to keep the most often accessed items stored on the SSD.  So while it is really two drives, a fusion drive for all practical purposes appears as a single drive.  One would have to get to the system level to see it as two drives and Apple has made that very difficult.  Accessing the drives separately is a quick and sure way to hose your system.

    mid-2010 27&quot; iMac, 16GB DRAM, OS X Mountain Lion, iPad '4'; ATV3; mid 2012 MBA;
  • MightyMac Level 1 Level 1 (45 points)

    I disagree with RAM being more important. Unless you run applications that are high end like Final Cut where you are rendering video on large projects or are planning on running VM for Windows with heavy multitasking in mind, 16GB of RAM will be a lesser return on investment. By the time your Mac will require 16GB of RAM, all the other components will be outdated anyways. Fusion Drive will have benefits to you all the time. It speeds up your Mac up to 3.5 times whenever it is accessed (launching apps, files, saving). It is a performance enhancement that you will actually use and feel more than the RAM. At least with the Fusion drive, if you happen to run out of RAM and page out, the disk performance of an SSD will be there to compensate for it. This question is getting asked a lot and I feel a lot of people are worrying about RAM that they will almost never use. If you needed 16GB of RAM, you would already know and wouldn't be asking. Get the Fusion, you will get performance that is up to date instead of an outdated 5400RPM HDD, and will make use of it very time you use your Mac. OS X is efficient enough in memory management, don't approach buying your machine with future proofing. Computers are outdated by the next refresh and you have to think about which specs provide the best benefit to you on a daily basis. On the 21.5" iMac, the Fusion should be the first priority. Never mind that you can't access the RAM. Unless you are using the machine for professional uses, which you would most likely be making money from it and choosing the 27" iMac, you do not need to worry about running out of memory. Your user experience will tangibly benefit more from Fusion, than it ever will from RAM.

  • MightyMac Level 1 Level 1 (45 points)

    Congrats Cameron! You will love the performance that will come with flash storage. Once you have SSD performance there is no going back. The difference is night and day. Once you have the machine, open the Activity Monitor and click the memory tab. You will see that the 8 GB of RAM is more than enough and you will feel even better about your decision. Enjoy your new iMac, they are wonderful machines and have been the cornerstone of my  Universe for years.

  • Jeff Nitschke Level 4 Level 4 (2,655 points)

    Ram (memory) is also really easy to add in the future & can be found really inexpensively from 3rd party resellers

  • Jeff Nitschke Level 4 Level 4 (2,655 points)

    I missed that. Sorry.


    I don't like how apple is limiting the upgrade-ablity of there new machines


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