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I've had a Windows 10 VM running for 10 days straight under 10.15.6 with latest VMWare Fusion. No issues so far, memory usage is typical. Will keep eye out for any weirdness but doesn't seem like this bug affects everyone, or every kind of VM anyway.
 
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Heavy VM user (crucial for my work) here.

Have had zero issues so far with this version on my Mac Pro, hope it stays that way.
 
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I'm on 10.15.6, using VMWare Fusion with Windows 10 VMs, and I haven't experienced this.
 
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My 2019 mbp 15" crashed and rebooted by itself on wake from sleep 2 days ago running 10.15.6. I really dislike using catalina. Crappiest macos in years. Fixes one bug and breaks 2 more other things. Not sure if it is related to this issue or not, but a fix should be on the way.
 
NO KIDDING - was on a call demoing to partners - when the whole system crashed. However, this bug did not just exist in .6. It is also present in .5 - experienced it multiple times with Fusion machines running.
 
Has anyone heard whether Apple Silicon Macs will run a Windows x86-64 VM on VirtualBox or Parallels?

I probably haven’t looked hard enough on the ‘net but I assume someone with a Developer Transition Kit has tested this?
You will be able to run Windows ARM natively and I am sure that it's going to get a lot of attention now that Apple is switching. The same will apply to all the Linux community, arm will get more emphasis. So, the future looks strong with a real competition to the stagnant x86
 
Having this issue since 10.15.6. Contacted apple about it, and again today. I have a calls setup with them at 1pm EST to review. Now, I'll bring this up as well. Since this is exactly what's happening to me as well. Each day using my VM's, everything is fine. Go home, come back to work. Crashed overnight. Same Kernel memory issue. I thought I was going to have to reinstall everything!! :) Thanks to VMware for confirming this and letting Apple know. Saved me a rebuild!
 
Still on Mojave. Everything rock stable. Large transfers? OK! VMware? Rock Stable. 32 bit/legacy? Hell yeah. Web browsers? works all the time.

Yup, and you know what else runs great?... a Catalina 10.15.6 guest running on a Mojave host with VMware Fusion. Rock solid host and guest[*] and very decent performance within the Catalina VM. My host machine is a 2016 MBP 15" with only 16GB RAM, so while I gave the VM 4 cores, I only gave it 4GB of memory. As long as I don't run too many apps within the VM, everything is all good.

Perhaps the only safe and sane Catalina is one that's caged up within a VM.

[*] Well, ok, to be clear the Catalina guest has been totally stable. That doesn't mean it's doing everything well; virtualized or not, it is still Catalina.
 
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Yup, and you know what else runs great?... a Catalina 10.15.6 guest running on a Mojave host with VMware Fusion. Rock solid host and guest and very decent performance within the Catalina VM. My host machine is a MBP 16" with only 16GB RAM, so while I gave the VM 4 cores, I only gave it 4GB of memory. As long as I don't run too many apps within the VM, everything is all good.

Perhaps the only safe and sane Catalina is one that's caged up within a VM.

Windows 10 also runs great...Getting used to it now for when my current MBP bites the dust.
 
I'm on 10.15.6 using VMWare Fusion running Windows Server 2019 and this issue has been driving me crazy. Glad its a known issue because I thought my computer was messed up. Hope they fix it.
 
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Question for Mac users, since Catalina has been famously buggy, what's there last best stable MacOS version?
Honestly, Catalina has been stable for me. From the variety of experiences people seem to be having, there’s no right answer to this.
Snow Leopard. Every MacRumors user's favorite $29 update to macOS.
I have zero issues with Mojave, from which I never upgraded predominantly because I’ve been too lazy to sort through my Apple for 64-bit compatibility (and, in retrospect, I’m glad I didn’t).

Mojave was stable from the very first beta, it is better than Snow Leopard, SL had big issues in the beginning, Mojave also has a lot more features.



Big Sur beta 3 has broken all virtualization software

My Mac crashed overnight running Parallels on Big Sur b2.
 
Question for Mac users, since Catalina has been famously buggy, what's there last best stable MacOS version?
Most probably Mojave. You don't want to be going too far back, as you need the latest security features. As other people have said, Mojave has everything you need from a modern OS.

That said, millions of people have been using Catalina with no problems. Running VMs is quite a power-user thing to do so if you only use your mac for basic everyday things - office apps, browsers etc, then you are likely fine with Catalina.

I stayed on Mojave myself firstly because my MS Office was still 32-bit, and secondly because of my Steam games catalogue. Now I'm on O365, and I haven't touched my 32-bit Steam games in over a year, I could probably go to Catalina right now and be fine. I probably won't though, I'm happy on Mojave for now and there's nothing I want in Catalina.

(I will probably upgrade my kids macs to Catalina for the improved Screen Time parental control functionality.)
 
Users of virtualization software have reported that macOS 10.15.6 crashes repeatedly when running virtual machines.

A regression in the App Sandbox component of macOS 10.15.6 is reportedly leaking kernel memory, causing macOS to crash. The purpose of an App Sandbox is to provide protection to system resources and limit an app's access to resources, such as memory.

VMware engineers have today diagnosed the issue and filed a "comprehensive" report with Apple, including a minimal reproduction case which should allow them to easily identify and address the issue. The engineer cautions that "it isn't looking good" going forwards, and it will likely fall to Apple to resolve the issue in a software update to macOS. It is unclear if this issue exists in developer and public betas of macOS Big Sur.

The workaround suggested by many users and VMware engineers is to refrain from installing macOS 10.15.6, or shutting down virtual machines when they are not in use and rebooting the host as often as possible.

Article Link: VMware Engineer Confirms macOS Catalina 10.15.6 Bug Causes Crashes with Virtualization
Not a VM user, but encountered 10.15.6 crashes repeatedly with last 2 public betas before it went to GM. What I noticed was my Apple Magic Bluetooth keyboard became unresponsive after kernel crash restart. I isolated this disabling Bluetooth in the system preferences, and not restarting, but power off, and then on. After that the 10.15.6 was stable using a USB keyboard instead. I reported this to Apple, and this news sounds very similar.

Note never encountered anything as bad as this issue in all the time I been testing public betas since the program has been going. Surprised it was released leaking kernel memory. Note using a late 2015 27” iMac, 4 ghz i7. Using a 2GB Fusion drive. Diagnostics showed no issues.
 
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