VMware Hypervisor/ESXi

Hypervisor Attributes

VMware ESXi/ESX 4.1

Citrix XenServer 5.6

Windows Server 2008 R2 with Hyper-V

Small Disk Footprint

70 MB disk footprint

(VMware ESXi)

1.8GB

>2GB with Server Core installation
 ~10GB with full Windows Server installation

OS Independence

No reliance on general purpose operating system

(VMware ESXi)

Relies on Linux in Dom
management Partition

Relies on Windows 2008 in Parent Partition

Hardened Drivers

Optimized with hardware vendors

Generic Linux Drivers

Generic Windows drivers

Advanced Memory Management

Ability to reclaim unused memory, de-duplicate memory pages, compress memory pages

Recently added basic overcommit, but does not adjust memory allocation based on VM usage; no deduplication or compression of pages

No ability to reclaim unused physical memory, de-duplicate or compress pages

Advanced Storage Management

               VMware vStorage VMFS, Storage vMotion

Lacks an integrated cluster file
system, no live storage migration, storage features support very few arrays

Lacks an integrated cluster file system, no live storage migration

High I/O Scalability

Direct driver model

I/O bottleneck in Dom0 management OS

I/O bottleneck in parent O

Host Resource Management

Network traffic shaping, per-VM resource shares, set quality of service priorities for storage and network I/O

Lacks similar capabilities

Lacks similar capabilities

Performance Enhancements

AMD RVI, Intel EPT large memory pages, universal 8-way vSMP, VMI paravirtualization, VMDirectPath I/O, PV guest SCSI driver

No large memory pages, no paravirt guest SCSI device, no direct I/O device support

Large memory pages,
4-way vSMP on Windows
2008 and Windows 7 VMs only

Virtual Security Technology

VMware VMsafe™ security API

Nothing comparable

Nothing comparable

Flexible Resource Allocation

Hot add VM vCPUs and memory, VMFS volume grow, hot extend virtual disks, hot add virtual disks

Nothing comparable

Only hot add virtual disks