Understanding XenCenter and XenServer products from Citrix


The virtual machine revolution and the virtualization market has several key players, including VMWARE (the market leader), Citrix (the most compreehensive offering), Oracle, (It has money to shop around for competitors, and bought Sun Microsystems and Virtual Iron in the last two years and it is hungry for more), Microsoft (has good offerings but lags Vmware and Citrix on key features).

Citrix has a virtualization platform that is really easy to use and it is great for test and production environments. Nowadays, any major company in the world should have some implementation of VMware and Citrix Virtualization technologies in place

On this article, I will concentrate on two Citrix offerings.

Citrix has two products that are related and they should be used in conjuction:
XenServer and XenCenter

XenServer is the physical environment where you load and host (store) Virtual Machines images for your virtual server farm. The software that runs the XenServer is Linux based (it uses some flavor of Red Hat). It is extremely easy to install (you can download an ISO image from the Citrix site) and has a semi-graphical interface that allows you to configure the network interface, password and other features.

Once you install the XenServer you can load virtual machines images (VMI) into it. But you need a tool to manage your VMI. This tool should allow you to create new VMs, add new storage, import VM images, reboot, shutdown, disconnect and reconnect your VM images, etc.
Citrix offers such tool and it is called XenCenter. XenCenter is a Windows based tool and it can be installed on your workstations (e.g. Windows XP and Windows 7)

XenCenter Overview:

“Your virtual machines are hosted using Citrix XenServer. Each virtual machine is an independent system called a guest operating system. Citrix XenCenter allows you to connect to the XenServer environment (just enter the IP address of the XenServer) and administer guest operating systems.

Once you are connected to your XenServer system, you will notice a list of guests in the left pane of XenCenter. Selecting a guest will allow you to monitor and administer it. The Console tab allows you to see the selected guest operating system desktop.

You can manipulate the console window to suit your preference. These are some useful functions available on XenCenter console:
Sending Ctr-Alt-Del to the guest VM to access the Windows Security Screen
Undock/redock (separate or join console screen)
Toggle full-screen mode
Scale the guest windows to fit inside the console window
Select a disk image to “insert” into the guest DVD drive
Toggle between VNC connection and RDP connection

This is a screenshot of a typical XenCenter interface screen. (there are five VM loaded):

Note that four VMS are loaded and active (they all have a green play button available) The fifth VM is in suspend mode and has a blue paused button(it is named WXPx64sp3). The center screen shows the VM called JP-AD1 in the log on screen
The active VMs are using real RAM from the XenServer and the suspended machine is idle and not using any memory from the XenServer. This is a nice feature available in the XenCenter. You can easily administer the amount allocated for each individual machine (See screenshot below)

I hope this helps you understand a little bit more about these two great Citrix tools

Note: part of this article was pasted from the Citrix documentation on XenCenter)

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Citrix’s definition: of Xen Server:
XenServer

“Citrix XenServer is a virtualization platform that provides open and powerful server virtualization. XenServer can reduce datacenter costs by transforming static and complex datacenter environments into more dynamic, easy to manage server workload delivery centers. It is based on the open source Xen hypervisor and delivers a secure and mature server virtualization platform with near bare-metal performance.
XenServer Components

XenServer consists of the following components:

XenServer host
The software installed on a physical server that is dedicated entirely to hosting virtual machines
The XenServer host controls the interaction between the virtualized devices seen by VMs and the physical hardware.
XenCenter
The software used to manage the XenServer host
This software can be installed on any system running a Windows operating system and can be used to run other applications simultaneously.” (excerpt from Citrix Courseware)
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