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My Laptop Specs : 8 GB RAM, 2 GB Graphics Card.

Host Operating System : Ubuntu 14.04

VirtualBox Version : 4.3.10

Guest Operating Systems : Windows 7 (with 4GB RAM) & Kali Linux (with 3GB RAM).

Queries :

  1. What is the maximum limit of Operating Systems that can be installed on Virtual Box?
  2. If i want to install another OS (with 4 GB RAM) in Virtual Box, will it effect my Host OS performance ? If so, please suggest the good solution.
  3. What will be my Host OS performance after installing two or more OS in VirtualBox.
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  • You should be able to install as many Guest OS's as your HDD has space for. Unless you're planning on running them in tandem, performance shouldn't be affected. – amanthethy Oct 4 '14 at 8:50
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  1. There is no maximum limit of OSs that can be installed in VirtualBox.

  2. Since all virtual machines are separate from each other, there will be no effect on host OS performance if you install another OS in VirtualBox unless both guest OSs are running at the same time.

  3. With 8GB of RAM there should be minimal or no effect on host OS performance after installing two or more OS in VirtualBox, unless you are running multiple guest OSs at the same time.


Other considerations related to performance of the guest OS in VirtualBox

  1. Your guest OS's performance will be better if your guest OS has a lightweight desktop environment. For example, Xubuntu has better performance in VirtualBox than Ubuntu. Disable the Aero desktop experience in the Windows 7 guest OS. Fancy desktop effects use more RAM, which is a limited resource that you can't afford to waste.

  2. Your guest OS's performance will be better if you give the guest OS enough RAM. 2GB of RAM should be enough give the guest OS good performance under normal circumstances.

  3. A virtual machine installed on an SSD has better performance than a virtual machine installed on an ordinary spinning disk HDD.

  4. VirtualBox is frequently updated and occasionally there are small changes in the VirtualBox GUI. If you are following instructions from a tutorial about how to install a guest OS in VirtualBox, make sure that the tutorial is a recent one.

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  • Hi @karel. So, RAM is only shared between Guest OS (or OSs) and Host OS, Right ? 1. If i allocate 8 GB RAM to Guest OS (Kali Linux) and if i run that only Guest OS for an instance , will it burden my Laptop ? (P.S : My laptop's RAM Capacity is 8GB). 2. If i allocate 6 GB RAM for 1 Guest OS and 4 GB for another Guest OS, and if i run those simultaneously, what will be its effect on my Laptop? – sr1 Oct 5 '14 at 15:16
  • The host OS and the guest OS cannot share RAM. Also a guest OS cannot share RAM with another guest OS if both of them are running at the same time. RAM must be allocated by giving part of the RAM to the guest OS and the rest of the RAM to the host OS. Your host machine has to run its own operating system plus the container for the guest OS. So if you have 8GB of RAM, give the host OS 4GB and there should be no problems with the host running out of RAM. – karel Oct 6 '14 at 13:22
  • Here are some examples of RAM allocation. Host OS 4GB, Windows 7 2GB and Kali 2GB. Or if you never run Windows 7 and Kali together you can use this allocation: host OS 4GB, Windows 7 4GB and Kali 4GB. I normally allocate 2GB to every virtual machine in my virtual machine library and I never use more than one virtual machine at the same time. This runs like a champ, however you should note that all of my virtual machines are stored on an SSD for better performance. It also depends on what you use the virtual machine for whether you can get much better performance from using an SSD. – karel Oct 6 '14 at 13:22

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