Running multiple VMs on same host - h/w error?

[johnnyt29]

I got two VM's to start on a Windows Server 2012 Essentials R2 running Workstation 12 player but after about 4 hours of running fine there was a Machine_Check_Exception - hardware problem (would have been Purple Screen of Death on my ESXi Server.). I restarted machine plus one VM but left the second VM off and everything has been fine (as it was before I tried running a second VM).

Is it okay in principle to have two VM's running on same host, provided there's enough RAM for both with some left over for the host (there was)?

Do I have to be careful how I allocated vCPU's? I have 4 cores + hyper threading (8 available logical cores) and had assigned 4vCPUs to each VM? Do I need to make sure I leave at least 1 vCPUs free or something, i.e. should I set vCPU to 2-3 to one or both VM's?

HW: one month old Intel NUC i5 w/vPro, 16MB RAM, 250GB Samsung 850 PRO (OS, apps and VM's) + USB 3 external hard drives for data (not used by VMs)

[johnnyt29]

I know this could be lots of stuff, much of it unrelated to vmware.

Just for basic principles troubleshooting:

1) can I run 2 VM's using VMware Workstation 12 on one host?

2) do I have to limit the number of vCPU's (below max) for each of those VM's on that one host?

3) do I want to limit the number of vCPU's for each of those VM's on that one host?

No need to answer all questions or elaborate. I'll take anything at this point.

Thanks

[dariusd]

1) Yes, easily, as long as your hardware is powerful enough.  On my system, I'll often run 10 VMs concurrently in Workstation.  There is a hard limit, though... it does depend on your host operating system and its configuration as well as the VMs you're running, but that hard limit might be around 40-64 concurrently-running VMs.

2) Yes.  As an upper limit, on Workstation, you have to set each VM's Total processor cores to no more than the number of total cores in your host system.  Very high core counts might lead to an overall reduction in system performance, though.  It's best to leave at least one processor core free for the host OS to use.

3) Yes.  Don't give a VM more processor cores than it can fully utilize.  This is usually a process of trial-and-error.  If your Windows Server 2012 R2 VM won't be used for intense computational workloads, 2 processor cores should be adequate.

A Machine Check exception is almost always a physical hardware failure.  From the symptoms you describe, I'd suggest three things...

1. Check that you have the latest firmware update installed on your NUC.  Some CPU microcode problems will manifest as Machine Checks, in which case a host firmware upgrade will deliver newer microcode which might help.

2. Download and run MemTest86 (Free version) or MemTest86+ and use them to test your system's RAM.  (It's a good idea to do this on any new system.)

3. If it only fails when the system is running two VMs, maybe your system is overheating.  Check for adequate airflow around/through the system.

Cheers,

--

Darius