Fusion drive questions

Discussion in 'iMac' started by maflynn, Dec 1, 2015.

  1. maflynn Moderator

    maflynn

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    #1
    I'm sure I'll sound like a noob on these questions but being new to the fusion drive technology. Is there any way (or an app) to determine what's currently on the flash portion of the drive?

    Also is anyone tempted to split up the fusion drive and run a traditional physical layout, i.e., one flash drive and another hard drive arrangement. If so what's the advantages of that?

    So far I'm happy with how my iMac is performing, and the 2TB Fusion drive is fairly quick - other then running it in windows. Booting up on that is SLOOOOWWWW, but that makes sense since the OS is sitting on the 5400 rpm drive.
     
  2. Samuelsan2001 macrumors 603

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    Oct 24, 2013
    #2
    Well you could split the fusion and then put both OS's on the SSD but other than that I can't see any upside with having to manage which drive your files are on.
     
  3. maflynn thread starter Moderator

    maflynn

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    #3
    I don't use windows enough to really justify that action and the 2TB fusion drive only has 128GB of flash AFAIK, so that would be tight to run OS X and windows.
     
  4. Samuelsan2001 macrumors 603

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    #4

    I can't really see an upside then to be honest, it's just creating more work for yourself.
     
  5. maflynn thread starter Moderator

    maflynn

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    #5
    These are just questions that's all. I'm also curious to see if there's any way to know what's on the flash portion of the drive as I mentioned
     
  6. Samuelsan2001 macrumors 603

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    #6
  7. joema2 macrumors 65816

    joema2

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    Sep 3, 2013
    #7
    The previous 4.x version of iStat Menus would show how much I/O was happening on the SSD vs HDD portions of FD. They removed this in ver 5. I have asked them multiple times to restore that feature, so far without success.
     
  8. bent christian Suspended

    bent christian

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    Nov 5, 2015
    #8
    Knowing which files reside on the SSD and which reside the hard drive has little useful purpose for most (almost all) users. It will only serve to activate latent OCD tendencies...which is what the Fusion drive exists to combat against.

    Just relax.

    Use the machine.

    Get your work done.
     
  9. makrom macrumors regular

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    Nov 4, 2015
    #9
    I understand why people would like to know that for sheer curiosity. But unless things aren't working as desired, I consider it a total blessing to not having to take care about so many things just for stuff to work propperly.

    When it comes to FD, people around here seem to be very interested in how exactly it works, how it could theoretically be tweaked and so on.
    This doesn't seem to apply to other technically encapsulated aspects though. I don't think anyone ever thought about customizing the OS X thread scheduler or memory manager to be more in line with one's preferences, unless there was a good reason to do so.
     
  10. Weaselboy Moderator

    Weaselboy

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    #10
    There is no way I have ever seen to tell what is on the flash portion and what is on the hard drive portion. Fusion works at the block level and not the file level, so I don't see how it would be possible to tell.

    You can kind of indirectly tell what is there.

    Run this (below) command in Terminal and it will give you a live feed of sorts of physical disk activity. On your Mac with Fusion you should see two physical drives in the Terminal output. Now launch say Safari and watch which physical disk has data IO. If the bulk of the IO is on the flash disk, that tells you most of Safari was on the flash side. I might be more interesting with something larger like your Lightroom library.

    Code:
    iostat -w1
     
  11. maflynn thread starter Moderator

    maflynn

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    #11
    I understand it may not be useful, at least to you but I am curious. What's wrong with trying to see how your system is working. I am using the iMac and I'm getting my stuff done, but like I said that should prohibit me from learning how the iMac works :)

    Thanks, that was helpful, though as you mention, it is indirect
     
  12. laragheast macrumors member

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    Jun 22, 2015
    #12
    Hi
    I have a 1 TB late 2014 iMac 5k fusion drive and I also wanted to split the fusion but did not want to chance it, so I think I worked away around it (I think ) I only had 32 GB on the system and I read some were that OS X fills the Ssd part first and leaves 4 GB Free and then the hdd so I partitioned the the fusion drive in disk utility leaveing the first part 120 Gb and named it Ssd and then the remainder 1tb hdd, I then copied over my sons cartoons about 200 GB on to the hdd side and left all the apps on the ssd side . I would rather it this way unless someone tells I am silly and that is this is not possible . I ran blackmagic on the both the Ssd and hdd and the Ssd has read around 600 and write around 300 the hdd has around 200 read and write .
     
  13. twilexia macrumors 6502

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    Oct 16, 2015
    #13
    I thought the 2TB fusion drive runs the 7200 rpm drive?

    I think a fusion drive benefits greatly from having an external "working" drive. For example, a 256GB Samsung T1 SSD. For working projects you put them onto the SSD. Then with the fusion drive you use that to run applications (coming off the SSD portion) and store files for backup.
     
  14. maflynn thread starter Moderator

    maflynn

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    #14
    I couldn't find any links and I thought it was 5400 but in the system profile I see its being listed as
    ST2000DM001
    2015-12-02_06-12-30.png

    Googling that, it comes up as a Seagate 7200RPM drive, so you may be right.
     
  15. bent christian Suspended

    bent christian

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    Nov 5, 2015
    #15
    I am pretty sure this is only on the 27" model. It looks to me like the 21.5" gets 5400RPM drives as base, and for any Fusion.

    (scroll to Storage)
    http://www.apple.com/imac/specs/

    27" looks like it gets 7200RPM as a base, and for any Fusion.
     
  16. twilexia macrumors 6502

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    Oct 16, 2015
    #16
    Are you absolutely sure about that? Apple has been rather sparse with details about the HDD portion of their FD, but I recall reading reports that the 1TB Fusion has a 5400 RPM while 2TB/3TB fusion has a 7200 RPM. I could be way off base though.
     
  17. bent christian Suspended

    bent christian

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    Nov 5, 2015
    #17
    I am not entirely sure, but I think it is unlikely given the business model. We know Apple likes to use as many interchangeable parts as possible. If Apple were to use 7200 RPM drives in the 21.5" 2TB Fusion, it would be specific to that one, single model. The 27" iMac takes a 3.5" drive hard drive. There is no room in the 21.5" model for that size drive. The two drives could not be interchangeable.
     

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