Citrix's no-cost XenServer 5.5 stacks up well compared with VMware's freely available ESXi; adding the $2,750-per-server Enterprise edition or the $5,500 Platinum edition bumps XenServer 5.5 into vSphere 4 territory.
The Essentials pack provides high availability, dynamic workload management and a host of other features; the Platinum edition adds a year of free upgrades along with automated virtual lab management and physical machine load balancing.
To put the two platforms in perspective: VMware vSphere 4, released just over two months ago, enables active virtual machines to migrate from one physical host to another without interruption, even when those physical systems are using different CPU models from the same manufacturer. Citrix XenServer requires that hosts in a resource pool have the same vendor, model and features. VMware significantly advanced virtual networking in vSphere 4 by providing a distributed vNetwork switch. VMware also now enables third-party switches to be integrated within vSphere 4. XenServer still provides all networking services within its virtual infrastructure.
All that said, for data center managers with modest-sized installations and restricted budgets, Citrix XenServer 5.5 along with the Essentials kit isn't a bad way to get started.
XenServer 5.5 to the Test
I installed XenServer 5.5 on a Hewlett-Packard DL360 G6 and an HP DL380 G6, as well as on a Sun Fire x4170. Each was equipped with a similar-model Xeon 5500 family processor and 12GB of RAM. The HP DL380 and the Sun Fire x4170 had four NICs, while the HP DL360 had two NICs. This equipment group met the basic minimums to form a XenServer resource pool.
I used OpenFiler, in the form of a Xen-compatible virtual appliance on the Sun x4170, to create a modest-sized 500GB iSCSI shared storage repository for the VDI (virtual disk image) files used by the virtual machines.
I was able to use the Windows-based XenCenter 5.5-the management interface for XenServer-to integrate my resource pool with Microsoft Active Directory to facilitate the authentication process for my XenServer administrators. It was a straightforward process to join the AD domain. While this makes it possible to use commonly available user provisioning tools to manage who has access to the XenServer console, I would like to see more granular administrative controls added to XenServer, such as those found in VMware's products. As it is, all administrators can access any functions in XenServer.
Citrix has changed the way virtual machine backup and snapshots are performed. It's now possible to take a snapshot from the XenCenter management console, in addition to using the extensive CLI (command-line interface). Snapshots are simple to kick off, requiring only a unique name to start the process. The CLI facilitates scripted backup and restore operations on the virtual machine inventory.
With Version 5.5, XenServer now offers support for Red Hat Enterprise Linux 5.3, Novell SUSE Linux Enterprise Server 11 and Debian Lenny. XenCenter also now provides a view that puts resources such as physical hosts, virtual machines, snapshots and storage repositories into folders, and resources can be tagged to create groupings of resources for reporting purposes.
Technical Director Cameron Sturdevant can be reached at email@example.com.