Parallels VM on 8GB MacBook

Mike Boreham

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I have often seen it said that if you run VMs you need 16GB. I understand the logic, and in principle it is obviously correct.

But I haven't got 16GB and I do occasionally run Windows 10 in Parallels 14 with so little problem that I decided to benchmark my 8GB base model 2017 MacBook. I have been considering getting a maxed out 12" MacBook, so this is part of that decision making process.

Parallels was set to use 4 cores, 3232MB RAM, 1GB of VRAM

Geekbench: 5660
Cinebench R15: 226
Cinebench R20: 417

Activity Monitor Memory pressure reached 75% during the above.

Not gaming performance but plenty for occasional productivity apps which is why most people use Parallels.

I didn't test Mac performance at the same time, and I didn't run any high RAM windows apps.

Is the recommendation for 16GB based on running more than one VM at a time, or wanting more performance than these benchmarks, or maintaining Mac performance at the same time?
 
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keysofanxiety

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Nov 23, 2011
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Is the recommendation for 16GB based on running more than one VM at a time, or wanting more performance than these benchmarks, or maintaining Mac performance at the same time?
A lot of it is down to classic recommendations. VMs use lots of RAM, so if you're going to be using VMs then 16GB would be best to err on the side of caution.

However you're absolutely right: VMs run astonishingly well on macOS with 8GB RAM. The memory management on macOS is so well optimised.

And of course people on forums generally come for advice. If they mention they're using VMs and want to know which Mac to buy, 16GB is always a good recommendation. Plus if they're really looking to futureproof then 16GB is a much better shout: even if for a lot of use cases it might not be necessary today, who's to say what tomorrow brings.
 

Mike Boreham

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A lot of it is down to classic recommendations. VMs use lots of RAM, so if you're going to be using VMs then 16GB would be best to err on the side of caution.

However you're absolutely right: VMs run astonishingly well on macOS with 8GB RAM. The memory management on macOS is so well optimised.

And of course people on forums generally come for advice. If they mention they're using VMs and want to know which Mac to buy, 16GB is always a good recommendation. Plus if they're really looking to futureproof then 16GB is a much better shout: even if for a lot of use cases it might not be necessary today, who's to say what tomorrow brings.
Perhaps another example where people chose higher specs than they really need...of which I have been plenty guilty in the past. Better to err on the side of too much than too little.
 
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thera

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Jul 19, 2012
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8GB ram is enough, for light use, problem is energy drainage when on batteries, just my experience from MBP 2012
 

bill-p

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It's multiple factors, many of which you won't see now but will creep up eventually. Here are a few:

1. Forcing VM use on 8GB makes it easier to hit swapping. Swapping makes the SSD wear out faster. Considering the SSD is soldered on, when they go bad, all you can really do is toss the computer in the trash. And no, I'm not just scaremongering.

2. Even if you don't care that the computer gets tossed in the trash, swap makes it so you lose free storage space that can be used for something else. As you continue to use a computer, it will accumulate your personal documents, music, etc... and eventually you will run out of space. So any little bit helps.

3. With more and more web technologies being introduced, websites and web browsers are starting to become heavy resource hogs. I can very easily write a website that will hog over 1GB of RAM just by itself (no need for 20 Safari tabs). Open about 3 tabs pointing to the same site, plus run VM and you'll see your Mac hit swap. Then problem #1 and #2 will creep in. Hell, with the Electron framework becoming more popular, eventually even your desktop apps are glorified websites. I am not kidding. Did you know the Slack app uses Electron? No? Watch its memory usage. Fun stuffs.

So the trend is to use more memory, and as much memory as possible. MacOS is fairly optimized but it's not the nimble lightweight little thing that it used to be, back in the Snow Leopard days.

Right now, 8GB is the new 4GB, and I honestly just had this same debate (8GB vs 16GB) over in the MacBook Pro section.

The thing is... 16GB is just superior. Period. If not because of necessity then because of peace of mind, knowing you won't run into unforeseen incidents due to lack of memory at some point.

If Apple still allows us to upgrade SSD and memory in the MacBook, nobody would tell you go for the 16GB model to begin with.

But alas, they don't.
 
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Neodym

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I only disagree on one point with you: While the MBP is a powerhouse that may easily outlast Ram boundaries in terms of performance, the 12" rMB is taking quite some compromises in the performance section to achieve it's ultra-mobility.

Chances are that performance of the 12" rMB will be insufficient at the time you hit the 8GB Ram barrier, so you'll probably want a newer machine anyway by then (fringe cases - especially with VM's - notwithstanding). On the rMBP the CPU's have much more reserves for many years to come, so imho it makes more sense to try to future-proof those machines.
 

Mike Boreham

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I only disagree on one point with you: While the MBP is a powerhouse that may easily outlast Ram boundaries in terms of performance, the 12" rMB is taking quite some compromises in the performance section to achieve it's ultra-mobility.

Chances are that performance of the 12" rMB will be insufficient at the time you hit the 8GB Ram barrier, so you'll probably want a newer machine anyway by then (fringe cases - especially with VM's - notwithstanding). On the rMBP the CPU's have much more reserves for many years to come, so imho it makes more sense to try to future-proof those machines.
Thanks Neodym, can I just paraphrase that to make sure I understand.

By the time a 12" MacBook is limited by 8GB it will also be limited in other respects, so need replacing.
When an MBP becomes limited by 8GB, it will not be limited in other aspects, so it is more sensible to get 16GB on an MBP than a MB.
 

EugW

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Jun 18, 2017
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Geekbench may not really be that useful as a test for VM performance. While CPU speed is important, IMO memory amount is more important than CPU speed in many cases. Well, it depends on what you use the VM for. If you're using it for Windows-specific low impact business software, the speed will be acceptable on a 2017 MacBook, as long as you have sufficient RAM, since the 2017 models actually have decent performance. (The 2015 model is slow, and while the 2016 is faster than the 2015, it is still slower than the 2017.) 8 GB is doable but is extremely limiting. 16 GB is far, far better. But if you're stuck with 8 GB, just be frugal in the way you allocate RAM to the VM, and how you use your machine. eg. 3 GB for the VM if you can get away with it, instead of 4 GB. As for Geekbench, the performance you'll get out of it should be the same whether it's an 8 GB Mac or a 16 GB Mac, because if all you're running is Geekbench, you won't be RAM limited. But if you're doing other stuff, that 8 GB will get eaten up quickly.

The other point is that even outside of VMs some applications that don't require much CPU performance still eat gobs and gobs of RAM. Some are due to the way they are designed, and some are just because they have design flaws, like memory leaks. For example, with extended usage, I can get MS PowerPoint to use over 3 GB RAM with just one presentation open. I suspect it is a memory leak but the bottom line is that while it will slow down a 16 GB MacBook, it's much worse on an 8 GB MacBook.

Note that my original plan in 2017 was either just get a 16 GB MacBook, or else perhaps get an 8 GB MacBook and then upgrade in 2020 after it went quad-core. In the end I was convinced to get the 16 GB up front and I'm glad I did because of the above MS Office behaviour and because there will be no more Intel MacBooks made, as this entire line has been discontinued, and I am totally uninterested in the MacBook Pro and MacBook Air lines. I'm going to use this 16 GB 2017 Core m3 MacBook until it breaks, or until several years after the first ARM MacBook is released.

I will also be waiting for a 6 GB iPad Pro, but I don't bother using MS Office on iPads. I find Office still isn't ideal on a touch interface, so I continue to do Office stuff on the Mac (or a Windows PC).

BTW, I tend to multi-task more with a multi-screen setup. It will be interesting to see how much more multi-tasking I'll do on the road with iPadOS + Catalina with Sidecar. I can tell you Sidecar works beautifully on my 2017 16 GB 12" MacBook with my iPad Pro 10.5 for a low latency dual-screen setup with excellent image quality, all for a weight that's the same as a 13" MacBook Pro. MS Office is much more pleasant with dual screens, in combination with a trackpad.

tl;dr:

If you're going to run a VM, most definitely get 16 GB RAM if possible. If you're stuck with 8 GB, you can still run a VM, but it will be quite a limiting setup and you'll have to work around that limitation.

Also, benchmarking with Geekbench often isn't really going to give you a realistic estimate of overall performance, because RAM may be the bigger limiting factor here, esp. if you're talking about a 2017 MacBook (which has significantly higher performance than the older models). You don't need much memory at all to run Geekbench, so performance in Geekbench on an 8 GB setup should be the same as in a 16 GB setup. But if you're multitasking with memory heavy stuff, then the 8 GB setup will often feel a lot worse than the 16 GB setup in the real world if you're running a VM.
 
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Mike Boreham

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Thanks EugW,

I take the point that RAM won't affect Geekbench. I included it as part of my general point that VM performance on 8GB 12" MacBooks is not as bad as might be expected from the universal advice to get 16GB RAM if you use VMs.

Obviously 16GB is going to be better. I really wanted to make the point that 8GB is better than I expected and may be enough for many people who might otherwise feel they had to have 16GB just because they run a VM.

As with most discussions of this nature, it depends on your usage and expectations.
 

EugW

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If I use just one application at a time on my old MacBook Pro, even 4 GB is actually fine. It’s actually quite responsive. However, once I start multitasking, even with just a few Safari tabs, along with email and perhaps Word, then things really start to lag at times. However, with 8 GB on the same machine, the experience is much, much better.

The problem with putting a VM into the mix is that once you allocate 3 to 4 GB to the VM, macOS is left with only 4 to 5 GB, analogous to my 4 GB Pro. Yes, it’s usable if you don’t multitask, but once you start multitasking to any significant extent, you’ll likely feel the RAM limitation.
 

Mike Boreham

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The problem with putting a VM into the mix is that once you allocate 3 to 4 GB to the VM, macOS is left with only 4 to 5 GB, analogous to my 4 GB Pro. Yes, it’s usable if you don’t multitask, but once you start multitasking to any significant extent, you’ll likely feel the RAM limitation.
Yes, multitasking is probably the most critical factor. When I am using Parallels I don’t usually run tasks on the mac, and I don't usually leave Parallels working in the background when I am using Mac. I can see 8GB could be limiting if you need to multitask.
 

SmackBookPro

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Jan 11, 2018
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I'm surprised just how well Parallels runs on my MacBook 2017 I just got. I didn't think it'd run at all to be honest, or be a 'frozen' situation if I tried. It's great for running Windows Excel whilst I work through my Excel Bible textbook on iBooks, flicking between the book and the VM is smooth. It's noticeably less smooth than my old 2018 MBP TB was, but that's to be expected. It's more than useable, if a little more affected by things like Windows Update and such in the background. I can sense that when I'm on Parallels that the Mac is completely orientated to delivering that experience, and that when I switch back to a more taxing task, say something like deleting a large folder, it'll put that on the burner for a while. For a little machine with no fan, I'm impressed!