SSD drives

Discussion in 'iMac' started by Antsz, Oct 25, 2018.

  1. Antsz macrumors newbie

    Antsz

    Joined:
    Oct 18, 2018
    Location:
    Manchester uk
    #1
    Hey :)

    I have an iMac 27" 2017 with a fusion drive. How can I get an SSD drive installed? Can I run an external SSD drive and if so what would you recommend?
     
  2. Fishrrman macrumors P6

    Fishrrman

    Joined:
    Feb 20, 2009
    #2
    Just wondering -- is it a 1tb or 2tb fusion drive?

    A fusion drive IS an SSD drive -- combined with a platter-based hard drive.
    TWO drives, "melded" into one via software.

    The problem with the 1tb fusion drive is the SSD portion is only about 32gb in size, and it quickly becomes "full", forcing much of "the action" to the HDD.

    The 2tb fusion drive model has a 128gb SSD portion -- much better.
     
  3. Antsz thread starter macrumors newbie

    Antsz

    Joined:
    Oct 18, 2018
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    Manchester uk
    #3
    It's a 2TB version mate, so would I not see a difference with a external SSD drive. I have 2 left over from when I broke my pc rig down last month
     
  4. ApfelKuchen macrumors 68030

    Joined:
    Aug 28, 2012
    Location:
    Between the coasts
    #4
    If you replace the internal 2 TB HDD with an SSD, there's little real point to operating it as a Fusion Drive - the Fusion drive would be moving data back and forth between an SSD and Flash storage - a lot of work for little benefit. The benefit would be to have a spanned volume - you'd manage the two drives as if they were one, rather than having to target data/apps to one drive or the other.

    Due to the way Fusion works, I'd leave the internal Fusion setup alone (Flash plus spinning HDD) - that gives you 2 TB internally that operates at near-SSD speed. Save the additional SSDs for external storage, so that your external store operates as well as your internal.




    I have to disagree with Fishrrman's description of how the 32 gb Flash in the 1 TB Fusion works. Afaik, he has yet to own a Fusion-equipped Mac, and there's little evidence from his postings that he's doing anything more than shooting from the hip when it comes to his understanding of how Fusion works.

    The Flash storage in a Fusion drive does not "fill," any more than the RAM in a system "fills" - its contents are constantly being refreshed, based on what data/code is being called by the CPU. Like RAM, the Flash does not hold entire files or packages - it holds only those blocks that are called by the CPU. Blocks that are regularly called are likely to remain Flash-resident. Blocks that are called once and not called again will likely be flushed, again, very much like RAM. In short, Fusion doesn't fill the 32 GB of Flash and then leave it there doing nothing while the HDD is actively thrashing. ("Filling the 32 GB of Flash and then leave it there doing nothing" more accurately describes what happens if someone "breaks" the Fusion drive into separate 32 GB or 128 GB SSD and 1-3 TB HDDs, manually deciding to place OS and major apps in Flash while leaving data and lesser apps on the spinning HDD.)

    What is true about his statement is that, if a person works with very large data sets, then 32 GB may be insufficient to hold all the frequently-used blocks. However, that's not the typical experience. Very roughly speaking, if a person gets good performance from an 8 GB RAM-equipped Mac, it's not likely that 32 GB of Flash will be over-taxed. On the other hand, if a user needs 32 GB of RAM ("need" based on actually monitoring Memory Pressure in Activity Monitor - not just based on ego or guesswork), then I'd agree that 32 GB of Flash for Fusion is probably going to provide sub-par performance. However, that performance does not routinely drop to HDD speeds; it'll still be calling most of the actively-used data and code from Flash.

    Now, I have a Late 2013, 3 TB Fusion Drive (128 GB Flash-equipped) 27" iMac at home. In routine use I can't notice the difference between that and the 2017 27" All-SSD Retina iMac I use at work. Think about it - many people use 128 GB Flash-equipped MacBook Airs - the entire contents of one of those machines would fit into the Flash of my Fusion drive. Do you think I really need 128 GB of Flash for actively used code and data? It hardly seems possible.
     
  5. Antsz thread starter macrumors newbie

    Antsz

    Joined:
    Oct 18, 2018
    Location:
    Manchester uk
    #5

    Sorry I meant running a SSD drive externally via usb 3.0 and not removing my fusion drive
     
  6. Fishrrman macrumors P6

    Fishrrman

    Joined:
    Feb 20, 2009
    #6
    You could try setting up an external boot SSD, getting it "in shape", and then doing some speed tests vis-a-vis the internal fusion drive.

    Something else you could do:
    Since the fusion drive is 2tb with a 128gb SSD portion, you could "de-fuse" the fusion drive.
    You would then have TWO drives in the iMac (128gb SSD and 2tb HDD).
    I'd then set up the SSD with the OS, apps, and basic accounts.
    I'd keep all my "large libraries" of stuff on the HDD.
    The iMac will then boot and run at the "full speed" the SSD can run (which is very fast on an iMac). Much faster than booting from ANY external SSD.
     
  7. mikehalloran macrumors 65816

    Joined:
    Oct 14, 2018
    Location:
    The Sillie Con Valley
    #7
    Any tech can do it in about an hour. Replacing both takes little more time than replacing one.

    Let's take a look at what you have.

    Your 2017 has two busses. The NVMe blade is on a PCIe 3x4 and it's screaming fast. You can get a 2T 970 EVO + adapter for $550–$600. Smaller costs less, of course. The bigger that is, the better the overall performance unless you just don't need anything that size.

    The other bus is SATA III. Replace the spinner with an SSD if you need more space. Li$t on a 2T 860 EVO is $349.

    You say you have a pair of SSDs — did I miss what type and capacity? Post what they are. If SATA, you can throw one in. If not, it depends on what it is but count on an adapter or two to make it work in the SATA buss (and some won't). You will not want to use it in the PCIe buss as it will slow down your Mac.

    You can certainly set up two SSDs as a Fusion drive but if the blade is large enough, there's little point. If throwing in a large SSD and leaving the 32G blade alone, I would do it on Mojave. High sierra does not support APFS on a fusion drive.

    Why replace the spinner? Heat and speed. Unless doing AV, heavy graphics, a DAW etc., heat is the more important reason. Your iMac will run cooler and quieter with less fan noise. Heat is also the enemy of long life for components.

    If 2T is a comfortable max for your system, replace the blade only and remove the spinner.
     
  8. Porkchop Sandwich macrumors regular

    Joined:
    Feb 3, 2017
    #8
    I appreciate the timeliness of this thread b/c I'd been wondering if the ssd side of a fusion drive could be replaced to increase its capacity due to the small size of the 1tb optioned ssd in a '17 fusion drive. Conceptually, it appears the answer's yes but, it would only make sense to do so if the drive was split per Fishrrman's dual drive scheme. Then, of course, the case for an external makes a ton of sense rather than fiddle with the internal.

    All that said, and please correct if I'm wrong; when installing windows on a fusion drive the os defaults to the hdd portion of the drive in its entirety, yes? If so, windows would run pretty slow I'd imagine. Also, I seem to recall that windows (10 in my case) cannot be s/u to run from an external - can someone confirm that? (haven't used windows with any regularity for yrs)

    What about windows on a fusion drive using vm? Windows still slow?
     
  9. ApfelKuchen macrumors 68030

    Joined:
    Aug 28, 2012
    Location:
    Between the coasts
    #9
    Can the "SSD side" of the Fusion be replaced/upgraded? The Flash storage blade is proprietary to Apple, and is not available from other sources. So, the only way to upgrade the blade is use a 128 GB blade salvaged from another iMac. You may also want to check ifixit.com for the procedure - it's rated "difficult," and for good reason.

    Again, because of the way Fusion works, "small" only matters if the way you use your Mac actually requires more Flash storage (see my analogies to RAM in previous posts). People look at "32 GB" and just assume they'll need more. It seems so pathetically small, but you could upgrade from 32 GB to 128 GB and never notice a difference in performance, just as many Mac users could upgrade from 8 GB to 16 GB or 32 GB RAM and not notice (or measure) the difference.

    Simple rule of thumb, whether you're talking about cars or computers - buy only as much capacity as you can practically use. If you do all your driving on city streets, you don't need a 12-cylinder racing engine. If the most cargo you carry is a half-dozen bags of groceries or a couple of suitcases, and you never have to seat more than four passengers, you don't need a seven-passenger minivan.

    Fusion exists to make economical use of an expensive commodity. It manages that precious stuff in ways no individual can achieve by splitting the Fusion storage into separate, manually-managed drives.

    Now, on to Windows...

    You're right. If you create a Boot Camp partition for Windows on a Fusion machine, it'll reside on the HDD. The Windows operating system does not support Fusion, so it has to work within the bounds of what it does support - a Windows-formatted partition. At that point, one of my basic rules of thumb takes over - the slower your HDD, the more RAM you'll want to have.

    You're basically right about not being able to boot Windows from an external drive. The Microsoft Windows installer does not want Windows to be installed to an external drive, and Apple's Boot Camp Assistant essentially respects that reality. However, there is a way (you can Google "Boot Camp on external drive"), which brings us to your next question...

    You can run Windows from an external drive by using VM. Windows will then run as quickly as the external HDD or SSD allows. Since the virtualization software would be running on the Mac (Fusion) partition, you'll see some performance benefits there, but since VMs place additional performance demands on the system, it's hard for me to say how much of a benefit it will be (although, obviously, the VM will run faster on a Fusion Mac than on an HDD-only Mac).
     
  10. mikehalloran, Oct 26, 2018
    Last edited: Oct 26, 2018

    mikehalloran macrumors 65816

    Joined:
    Oct 14, 2018
    Location:
    The Sillie Con Valley
    #10
    Says who? Apple? Did you miss when I wrote the following?

    The form of the original unit is proprietary, not the technology. In fact, Samsung makes both units. I just found the blade for $499 and the adapter for $6 this morning. You have to loosen the speaker to install but it tightens up again without an issue.

    The downsides are the cost and it will void your warranty.

    The upsides include saving a lot of money and being able to sell the system pull for $300–$1,000 depending on size. All 2015 and up Macs with a blade can all benefit from the old one as they have a PCIe 3x4 slot except the Mac Pro. The 2015 iMac has a PCIe 2 chip in a PCIe 3x4 buss.

    The Mac Pros still have a PCIe 2 buss. The 2017 chip will install but can't make it run faster.
     

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9 October 25, 2018