Hypervisor Attributes | VMware ESXi/ESX 4.1 | Windows Server 2008 R2 with Hyper-V | Citrix Xen Server 5.6 |
CPUs supported | Recent AMD, Intel | Recent AMD, Intel | Recent AMD, Intel |
# CPU cores supported | 64 | 64 | 64 |
Memory supported | Unlimited | 2TB | 256GB |
I/O devices supported | IDE, SCSI, SAS, SATA, FC, 1Gb and 10Gb Ethernet, iSCSI, NFS, FCOE, Infiniband | IDE, SCSI, SAS, SATA, FC, 1Gb and 10Gb Ethernet, iSCSI, CIFS, FCOE, Infiniband | IDE, SCSI, SAS, SATA, FC, 1Gb Ethernet, iSCSI |
Memory optimization | Over-commit, transparent page sharing, ballooning, large memory pages | Standard Windows Server 2008 features | None |
Platform support | Fewer vendors | More vendors | More vendors |
Supported storage of guest VMs | Direct, SAN, NAS, iSCSI | Direct, SAN, iSCSI | Direct, SAN, NAS, iSCSI |
Number of nodes in a cluster | 32 nodes if < 40 VMs per node | 16 | 16 |
Operating systems supported | Asainux, CentOS, Debian, FreeBSD, OS/2, Solaris 10, SCO OpenServer, SCO Unixware, Windows Server, RHEL, SUSE, MS-DOS, Netware | Windows Server, Vista, XP, SUSE Linux | All Microsoft And Linux Platform |
# virtual CPUs supported | 8 | 4 | 4 |
# guests per host | 256 running | 192 running | |
# Amount virtual memory | 255GB | 64GB | 64GB |
Virtual NICs | 10 | Yes, limit unknown | 16 |
Small Disk Footprint | 70 MB disk footprint (VMware ESXi) | >2GB with Server Core installation ~10GB with full Windows Server installation | 1.8GB |
OS Independence | No reliance on general purpose operating system (VMware ESXi) | Relies on Windows 2008 in Parent Partition | Relies on Linux in Dom management Partition |
Hardened Drivers | Optimized with hardware vendors | Generic Windows drivers | Generic Linux Drivers |
Advanced Memory Management | Ability to reclaim unused memory, de-duplicate memory pages, compress memory pages | No ability to reclaim unused physical memory, de-duplicate or compress pages | Recently added basic overcommit, but does not adjust memory allocation based on VM usage; no DE duplication or compression of pages |
Advanced Storage Management | VMware vStorage VMFS, Storage vMotion | Lacks an integrated cluster file system, no live storage migration | Lacks an integrated cluster file system, no live storage migration, storage features support very few arrays |
High I/O Scalability | Direct driver model | I/O bottleneck in parent OS | I/O bottleneck in Dom0 management OS |
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 Para virtualization, VM Direct Path I/O, PV guest SCSI driver | Large memory pages, 4-way vSMP on Windows 2008 and Windows 7 VMs only | No large memory pages, no paravirt guest SCSI device, no direct I/O device support |
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 | Only hot add virtual disks | Nothing comparable |