number of cpu and cores on an i7 physical machine

[stephanoirrs]

Hello,

I have a Windows 7 Pro physical machine running on an i7-4700MQ Intel processors with 4 cores (8 logical).

I have 3 VMs already set up, and working :  one is an XP Pro, the other 2 are Windows 7 Pro. 

They are all set up however to run with 1 CPU and 1 core.

It is OK for me to leave the XP Pro VM that way, but I think the two W7 VMs should get 2 cores each, therefore ending up with a config of 1 cpu & 2 cores in their VM settings. Each of these W7 VMs would end up being development enviroments, both ending up running an IDE, at least a database, a web server and a number of auxiliary apps, beside a browser and a mail client. In addition, I plan to have some parallel processing load running on these machines (e.g. map & reduce), therefore maximizing the number of cores for them would be desirable.

Overall, it would seem that the machine could bear the load, leaving one core to the physical machine.

Is this doable, advisable? Pros and cons? 

Thanks

[bgh89928]

I have I7 2600k, 32GB RAM, 240GB SSD and 3 x 1TB HDD,  I am running 3 VMs with Win7 installed on each HDD, totaling 9 VMs.  Each VMs are configured as 1CPU 1Core, 2GB RAM.  My VMs are on 24/7 since last November without any critical issues.

On normal days, CPU usage is not over 50% max, so I am planning to implement couple more VMs in near future.

I believe your system will handle 3+ VMs without any problem if you have enough RAM and disk size.  However, I would suggest if your VMs will cause lots of read/write action to the disk, install VMs on second disk drive, other than OS installed one.  Otherwise, it will cause slow performance / freeze on your VMs and your host.

Edit:  the number of CPU / cores you configured to VMs doesn't really take any CPU / core away from your total number of physical CPU / core.  It is logical CPU / core, unless your VM always uses 100% CPU power, you will always have more room on your physical CPU / Core usage than what you configured to .

[stephanoirrs]

bgh89928,

thanks for your reply, which has useful and informative elements.

Perhaps though you didn't address my main questions directly, namely whether it'd be ok to boost the number of cores for each of the two Win7 VMs to 2 -- I would indeed like to give these two VMs at least 2 cores / 4 logical cores, at the very least for the parallel processing tasks I intend to have them perform.

About the rest, I share indeed your suggestion to keep the VMs on a separate disk, which I am about to acquire -- I have been experiencing exactly the type of disk contention you suggested and it did take a good deal of monitoring and ... cursing to come down to that culprit.

Thanks again.

PS: I forgot to add, in my original msg, that the VMs are running under Workstation 7.1, should that be of significant relevance

[weinstein5]

Welcome to the Community - Worksation does a good job of scheduling the VCPUs - remembering that a VCPU can only run on a single LCPU so with 8 LCPU and assigning the 2 VCPUs to your VMs should not be a problem.

[stephanoirrs]

Thanks weinstein5 ,

when you say 2 VCPU, what configuration does this translate to in Workstation's terms?

In the setting you can specify # of CPUs and # cores:

you mean CPU = 1 and Cores = 2, correct?

[weinstein5]

LCPU - Logical CPU which is the term used for either a physical core or a Hyper Thread on a physical  CPU where the hypervisor will schedule a VCPU - so0 your machine has 8 LCPUs - where workstation will schedule the VMs VCPUs to run on those LCPUs - so yes in WS configuration for you VM 1 VCPU with cores will use two LCPUs

[bgh89928]

Thank you, weinstein5

another good knowledge learned from here.

[weinstein5]

Happy to help!

[dhh]

I just installed WS 11 trial version (to see what it looks like). The reason being I've been running 6.5 (sigh) and need to be able to create VM's with more than dual core.

Installed to laptop with i7, four cores/CPU's.

Created a VM. Selected four cores.

Got warning telling me the Host system does not have four cores.

Further interesting note: I originally tried Oracle VBox (free) and ran into exactly the same issue. Figured it was a bug in VBox and since it was free I wasn't going to get any help on it so I jumped to VMWare 11.

Same problem. Granted, VBox is clearly a pretty close copy of VMWare....

[dhh]

Reply to myself: i7-3540M has 2 "cores" with each core having 2 processors. So 4 processors, 2 cores. Now I need to go back and see the VMWare verbiage to know what VMWare is considering "CPU" to be.

Maybe  CPU=Core, not "processor".

[dariusd]

Go into your host's BIOS/EFI setup and check whether Hyper-threading (HT) is enabled.  If Workstation is complaining about insufficient cores when "Total processor cores" is set to 4 in your VM's configuration, it's likely that your host has Hyper-threading disabled, so only two cores will be visible to the host.  Enabling Hyper-threading will provide four cores.  (Enabling HT will probably get VBox working too...)

--

Darius