VMware VSphere vs. Citrix XenServer

When evaluating the pros and cons of Citrix XenServer compared to VMware vSphere ESXi, the first thing to note is that these two software systems are developed and supported by different companies. The VMware vSphere ESXi is developed by VMware Inc., whereas XenServer is developed by Citrix.

Though they perform similar roles, they do have a few distinct differences which make them unique. The main difference between the two is the intended usage of the software. The Citrix XenServer is used by personal users and small- to medium-sized businesses, while VMware vSphere ESXi is only intended for small- to medium-sized companies and is not structured for personal use.

Both of these software programs run the Bare Metal (Type 1) hypervisor type and support x86 and x64 architecture. Though they support various types of virtualization such as hardware-assisted virtualization and paravirtualization, only VMware vSphere ESXi does support full virtualization. Neither support was operating system virtualization, which you can learn more about in this article on VMware vSphere Best Practices.

Both software suites support a variety of storage options. The difference between them, when it comes to virtualization, is that VMware does support FCoE and SSD for Swap and does not support USB, SATA, SAS, NFS, iSCSI—which are all supported by Citrix XenServer. Both of them support DAS, FC, and NAS storage while neither of them supports eSATA or RDM. Both systems have also gained lots of users in the education, financial services, healthcare, and the government.

The Citrix XenServer and VMware vSphere ESXi pricing comparison offer a few interesting insights into the different business models that they have adopted. XenServer is open source and free and does provide per-server licensing.

VMware, on the other hand, requires a proprietary license and is licensed per processor. Both products do have a substantial client following dotted all over the globe irrespective of their pricing structure.

Both these software programs have a virtual disk size of 2000 GB, but the RAM per virtual machine does vary with VMware since it offers a staggering 1024 GB while the Citrix XenServer provides 128 GB per virtual machine.

The XenServer has a total of 16 Virtual CPUs per Virtual Machine (VCPUs), and VMware has doubled this, at 32 VCPUs. XenServer provides a total of 7 Virtual Network Interface Cards (NICs) per virtual machine and 16 virtual disks per virtual machine. On the other hand, VMware vSphere ESXi has a total of 10 virtual NICs per virtual machine and a massive 62 virtual disks per virtual machine.

VMware vSphere has a total of 120 (hundred and twenty) virtual machines per host with the RAM per host comprising at 2048 GB with a total of 2048 virtual disks per host.

Citrix XenServer has a whole pack of 75 (seventy-five) virtual machines per host with a RAM of 1024GB per host and 512 virtual disks per host.

Both systems have 160 (hundred and sixty) logical CPUs per host with the VMware capable of having a total of 2048 Virtual CPUs per host. However, XenServer does not have any virtual CPUs on the host.

One section where these programs tend to differ— and to a large extent explains the disparity in acceptance and usage levels between the two— is virtualization management.

The only important management feature that is approved by both software programs is Thin Provisioning.

While VMware does not help Asset Management and Configuration Mapping, Citrix XenServer does support these two management features in addition to Thin Provisioning but does not support critical functions such as Dynamic Resource Allocation, Failover, and Live Migration. These three essential features are on the other hand fully supported by VMware vSphere ESXi.

It should be noted though that if you are looking for other additional features such as Automated Workflows, High Availability (HA), Maintenance Mode, Shared Resource Pools and VM Backup / Restore then it is advisable to try out other software programs such as VMware vSphere Essentials.

The next area that differentiates the two is supported host operating systems. Without a doubt, the Achilles heel of VMware vSphere is the number of host operating systems supported by the program. VMware vSphere does only support MS-DOS and Free BSD as hosts.

On the other hand, Citrix XenServer does support a plethora of host operating systems such as Novell Linux Desktop, Red Hat Enterprise Linux AS, Linux ES, Linux WS and Red Hat Linux. Other OS supported include Windows 2000 Professional and Server, Windows 98 and 95, Windows Me, Windows NT Server, Windows NT Terminal Server, Windows NT Workstation, Windows Server 2003 Enterprise, Web and Standard Editions and Windows XP Home and Professional editions.

On this front, the Citrix XenServer vs. VMware vSphere ESXi battle is relatively even as they both support the following guest operating systems: Novell Linux Desktop, Red Hat Enterprise Linux AS, Red Hat Linux ES, Red Hat Linux WS ,Red Hat Linux, Windows 2000 Professional , Windows 2000 Server, Windows 98 , Windows 95, Windows Me, Windows NT Server, Windows NT Terminal Server, Windows NT Workstation, Windows Server 2003 Enterprise, Windows 2003 Web , Windows 2003 Standard, Windows XP Professional, and Windows XP Home Edition.

The exception, however, is that VMware supports MS-DOS, Sun Java Desktop System, and Solaris x86 platform edition as guest operating systems, while Citrix XenServer does not support any of these three operating systems either as the host or guest operating systems.

Both these software packages support a variety of technical support media such as forums, instructional videos, online self-service, knowledge base, system upgrades, telephone, and white papers.

They also differ in this area as VMware does not provide technical support via blogs, brochures, email, and owner’s manual but most importantly does have a well-staffed help desk and also offers a remote training option.

Citrix XenServer, on the other hand, does provide technical support through blogs, email, brochures, and user’s/owner’s manual—but does not provide this support through a help desk or remote training

Coming to the market behavior and recognition space, the VMware vSphere ESXi appears to win out over its competitor. Now that you know more about both products, you can determine which best fits within your career path.