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Guidelines for allocating system resources for VMs?

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  Guidelines for allocating system resources for VMs? Albin Otterhäll <gmane@otterhall.com> - 2016-05-14 11:10 +0200
    Re: Guidelines for allocating system resources for VMs? Martin Read <zen75502@zen.co.uk> - 2016-05-14 12:50 +0200
      Re: Guidelines for allocating system resources for VMs? Albin Otterhäll <gmane@otterhall.com> - 2016-05-14 13:40 +0200
        Re: Guidelines for allocating system resources for VMs? Linux-Fan <Ma_Sys.ma@web.de> - 2016-05-16 18:40 +0200

#167863 — Guidelines for allocating system resources for VMs?

I want to use virtual machines for my everyday work on my laptop (with a
Intel Core i5-3320M @ 2.60 GHz * 4 and 16GB RAM), using KVM on Debian as
my hypervisor.

But I can't find any general guidelines for how much system resources to
"give" to a VM. How many logical cores? How much RAM? Note that the
primary OS only should act as a hypervisor.

I will primarily use a Debian VM (i.e. Debian VM on Debian), but I also
want to be able to run a Windows 10 VM (Windows VM on Debian). It's not
necessary for both VMs to run simultaneously.
-- 
Regards,
Albin

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#167865

On 14/05/16 10:05, Albin Otterhäll wrote:
> I want to use virtual machines for my everyday work on my laptop (with a
> Intel Core i5-3320M @ 2.60 GHz * 4 and 16GB RAM), using KVM on Debian as
> my hypervisor.
>
> But I can't find any general guidelines for how much system resources to
> "give" to a VM. How many logical cores? How much RAM? Note that the
> primary OS only should act as a hypervisor.

How much RAM and how many cores do you think the work in question needs?

Answer that, and you have the basis for your answer.

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#167868

Martin Read:
> On 14/05/16 10:05, Albin Otterhäll wrote:
>> I want to use virtual machines for my everyday work on my laptop (with a
>> Intel Core i5-3320M @ 2.60 GHz * 4 and 16GB RAM), using KVM on Debian as
>> my hypervisor.
>>
>> But I can't find any general guidelines for how much system resources to
>> "give" to a VM. How many logical cores? How much RAM? Note that the
>> primary OS only should act as a hypervisor.
> 
> How much RAM and how many cores do you think the work in question needs?
> 
> Answer that, and you have the basis for your answer.
> 
> 
The thing is that I don't know (don't know how to access the necessary
information either), and assigning as much as possible would probably be
the best solution.

I plan in the future buy a GPU and use PCI passthrough to use a VM for
gaming, and then I would need to assign as much resources as possible.

-- 
Regards,
Albin

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#167912

[Multipart message — attachments visible in raw view] — view raw

[Sat, 14 May 2016 11:35:53 +0000] Albin Otterhäll <gmane@otterhall.com>
wrote:
> Martin Read:
> > On 14/05/16 10:05, Albin Otterhäll wrote:
> >> I want to use virtual machines for my everyday work on my laptop
> >> (with a Intel Core i5-3320M @ 2.60 GHz * 4 and 16GB RAM), using
> >> KVM on Debian as my hypervisor.
> >>
> >> But I can't find any general guidelines for how much system
> >> resources to "give" to a VM. How many logical cores? How much RAM?
> >> Note that the primary OS only should act as a hypervisor.

[...]

Well, the good thing about virtual machines is that you do not need to
really decide this now. Just start with a value you consider useful now
and later add more virtual memory and virtual CPU cores.

For Windows, I'd generally recommend you to expose 4 virtual cores and 6
GiB of RAM, for Linux, I'd go for 4 virtual cores and 4 GiB of RAM.

Apart from the applications you run, it highly depends on the number of
virtual machines running simultaneously. If you only ever run one of
them at once, give all your RAM minus about 1 GiB to them. If you run
some in parallel, distribute your RAM over them (If you use memory
ballooning, you can overcommit carefully).

For Windows, I usually give a bit more RAM than Linux, but it also
depends on what you do inside the VM. On your system, I'd minimally
assign 2 GiB for Linux and 3 GiB for Windows (if you intend to run
more than two VMs at once). Should you only want to run one Windows and
one Linux VM, you might as well give 7 GiB to Linux and 8 to Windows and
adjust as necessary later.

Normally, you can give each VM all of your CPU cores. This will result
in all VMs being able to access the whole computing power and if two
VMs try to access all cores at the same time, they will be scheduled
similar to processes in the OS.

As you can see: There is no clear recommendation -- just try out a few
configurations and settle for what works best :)

HTH
Linux-Fan

-- 
http://masysma.lima-city.de/

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