XenServer 5: First Impressions

Can 99% of the world’s cloud vendors be wrong? Is XenServer and its hypervisor technology the right answer for you and your virtual infrastructure? I’m taking XenServer 5 for a test drive to view it from a new user’s perspective and to answer these questions. This test drive begins with ISO image and software downloads from the Citrix website, proceeds through installation and update and ends with working with virtual machines (VMs). My purpose is to give you an overview of XenServer’s features and possibilities for your own trek into the world of virtualization.

The test hardware for this article is an AMD 64×2 4800+ with 3GB RAM and internal IDE and SATA hard drives.

Download and Installation

XenServer 5 is easy to find on the Citrix homepage — follow the link to the download area. At a minimum, you’ll need the XenServer 5 ISO, XenCenter 5, and the license to update your system from the Express Edition to the Enterprise Edition. Optionally, you might want the 250MB Linux Guest Support ISO file. This ISO image contains Linux VM templates and other useful tools for Linux VMs.

Save the license file (XenServer-free-license.xslic) from the download area onto your XenCenter Windows computer. This license enables you to use XenServer Enterprise Edition until April 23, 2009. The unlimited license key update will be available on March 25, 2009.

Once you download the 300MB XenServer ISO image and burn it to a CD-R, installation takes 15 to 20 minutes including the reboot and login to the XenServer Console (Shown in Figure 1). If you downloaded and burned the Linux Guest Support ISO image to a CD-R, the installer process prompts you for it.

Figure 1: XenServer Console Configuration

Local and Remote Consoles

XenCenter allows the most flexibility and feature rich experience for managing your virtual infrastructure. There are, however, two other consoles available to you; local and remote. The local console is available on the hypervisor computer itself. Enabling the remote shell service (SSH) provides you with shell (command line) access to the XenServer system and a duplicate of the Xen Console. To use the remote console, SSH to the XenServer computer, login and issue the xconsole command to invoke the console.

Using either the remote or local XenServer Console, you have limited functionality — in other words, you can’t fully manage a Xen hypervisor with one of these consoles but they provide important information about your system. For example, you enable SSH access via the consoles but you can’t create virtual machines with them. You have to use Xen Center for complete management capabilities and options. See Figure 2 for a look at XenCenter 5.

Figure 2: XenServer GUI

Virtual Machine Management

There are three ways to create VMs in XenCenter 5: Template, Import and ISO Image. The template method is by far the most efficient in terms of speed and configuration consistency. Anyone managing a Xen environment should implement operating system templates for all new VMs. When creating a template, remember to give the template image a generic hostname and a dynamic IP address to remove the possibility of duplicating one or the other on your network.

Creating a template from a “gold” or master image is an irreversible process so if you realize later that you’ve made a mistake in your master image, you’ll have to create a VM from the template, uninstall the template, fix the problem in the image and convert it once again to a template.

Disadvantages

Managing updates is awkward at best. To install updates, you have to download them onto your XenCenter (Windows) system then apply them using XenCenter under Tools->Updates Manager. Update configuration and management should be handled via a yum-style repository in an automated fashion. Another alternative is to configure update management similar to Windows updates with multiple possibilities such as download only, download and install and notify only.

Creating a new VM by the import method is somewhat disappointing because you only have the option of importing from a Xen VM exported image. To be a platform that companies switch to, XenServer needs the ability to directly import virtual machines from VMware.

Advantages

The greatest advantage is that XenServer installed perfectly on my test system — a feat still unaccomplished by VMware ESX and ESXi on the same hardware. That XenServer supports IDE and SATA drives is a huge advantage over VMware which only supports SCSI disks. VMware’s hardware limitations and significant price differential give XenServer a huge boost in the development and corporate sectors.

Like most of its competitor products, XenCenter is very easy to use. Creating VMs from templates or ISO images is a snap. Creating and working with Resource Pools is also very simple. If you’ve worked with VMware’s Virtual Center, you’ll appreciate XenCenter’s speed and simplicity. In a side-by-side comparison of setup and use, XenCenter and XenServer

Does XenServer 5 pass the “first impression” test? Yes. It offers speed, flexibility, scalability, ease of use, and a price that will make your accountant grin. XenServer 5 is a success from download to deployment and a win for Citrix and users alike. There’s much to like about XenServer 5 and very little to dislike. An enterprise-level product built by one of the world’s leading technology companies that’s also free — what’s not to love?