Virtual Machines & Build System Presentation (20-07-2010)


Few comments from Akshat

Regarding use of virtual box

I think use of VMWare Server or VMWare ESX Server is better. In VMWare, VMPlayer is equivalent of Virtual Box. However, if virtual infrastructure is required to be used for hosting servers, itís better to use VMWare Server due to the fact that in VMWare Server, the virtual machines can be run as a service. The effect of this is that, even after reboot the virtual machines will be running on their own like a normal service would run even after reboot. However, in VBox (and in VMPlayer too) all the machines will be required to be manually booted after every reboot of the host machine. However, they can always be put in start-up script though. Besides, VMWare server will provide a web-gui and remote console to manage the VMs from remote locations.

VMWare ESX Server or even XEN bare-metal solution, provide a more secure, better performance solution to the purpose. In this, there is no need of any host OS to be present. In this, in a way, the virtual machines run on the hardware (bare-metal) directly and thus give better performance and are also more secure. This solution though has two things to be foreseen:

  • Drivers could be an issue. However, now-a-days most of the hardware used is from a well-known subset and VMWare ESX Server supports quite a lot
  • There is nothing like a desktop for VMs over here. The virtual machines will be running but one will not be able to see the desktop (either GUI or command line) by logging on to the system. To do that, a software known as VMWare ESX client comes and using this only all the installation and monitoring can be done

Regarding CERN-ONLY repo access

This need to be checked as exactly where is the problem. Network wise this should be possible as for CERN machine means IP address and Mac Address and not the physical machine.

I, alongwith Marco, checked it on virtual machine having hostname as dashb-virtual08. We were able to get access to CERN-ONLY repo. We installed a package to confirm the same.

Regarding Performance

Bare-metal solution will give the best performance always as there is very less overhead in passing the system calls from virtual machine to the hardware. This is because, as obvious, due to the absence of host OS. However, even the other solutions donít degrade performance that significantly specially when used with hardware which have CPUs with virtualisation support. The virtualisation overhead over performance is significant when the CPU load on N or more virtual machines reaches at high level at any instant on the system having N CPUs and each virtual machine is configured for using 1 CPU. If normal load on the servers is not much, and peak are expected at very rare instants and that too not on all at the same instant, it might be better to have each of the N virtual machines (on a system with N CPUs) configured for more than 1 CPU. Here, we will have more potential to handle peak loads and also better performance. Besides, following configuration can always increase performance, apart from having more and upgraded RAM and upgraded CPU :

  • Disable devices like com1, com2, lpt1, cdrom and usb if not used regularly. Then can be enabled as and when required. This frees up some IRQ resources and hence IRQ conflicts are better handled.

  • Have swap partition on other physical hard disk of the host.

  • Distribute virtual disks within the same VM across multiple physical hard disks.

  • Minimise graphics features.

  • Run VMWare tools for VMWare or Guest Additions for VBox.

-- MarcoDevesasCampos - 21-Jul-2010

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Topic revision: r3 - 2010-07-26 - AkshatKakkar
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