ESXi and ESX Architectures Compared

VMware ESX Architecture. In the original ESX architecture, the virtualization kernel (referred to as the vmkernel) is augmented with a management partition known as the console operating system (also known as COS or service console). The primary purpose of the Console OS is to provide a management interface into the host. Various VMware management agents are deployed in the Console OS, along with other infrastructure service agents (e.g. name service, time service, logging, etc). In this architecture, many customers deploy other agents from 3rd parties to provide particular functionality, such as hardware monitoring and system management. Furthermore, individual admin users log into the Console OS to run configuration and diagnostic commands and scripts.

VMware ESXi Architecture. In the ESXi architecture, the Console OS has been removed and all of the VMware agents run directly on the vmkernel. Infrastructure services are provided natively through modules included with the vmkernel. Other authorized 3rd party modules , such as hardware drivers and hardware monitoring components, can run in vmkernel as well. Only modules that have been digitally signed by VMware are allowed on the system, creating a tightly locked-down architecture. Preventing arbitrary code from running on the ESXi host greatly improves the security of the system.

Understand the Difference between ESX and ESXi

VMware ESXi is VMware’s most advanced hypervisor architecture. Learn about the differences with the previous generation architecture, VMware ESX:

See the KB article for a detailed comparison.

Compare ESXi to Other Vendors' Offerings

Hypervisor Attributes	VMware ESXi 5.0	Windows Server 2008 R2 SP1 with Hyper-V	Citrix XenServer 5.6 FP1
Small Disk Footprint	144 MB disk footprint (VMware ESXi)	>3GB with Server Core installation ~10GB with full Windows Server installation	1GB
OS Independence	No reliance on general purpose operating system (VMware ESXi)	Relies on Windows 2008 in Parent Partition	Relies on Linux in Dom0 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	Only uses ballooning. No ability to de-duplicate or compress pages.	Only uses ballooning. No ability to de-duplicate or compress pages. Does not adjust memory allocation based on VM usage.
Advanced Storage Management	VMware vStorage VMFS, Storage vMotion, Storage DRS	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 32-way vSMP, VMI paravirtualization, VMDirectPath 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, Requires inflexible SR-IOV
Virtual Security Technology	VMware VMsafe™ Enables hypervisor level security introspection	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
Custom image creation and management	VMware Image Builder allows administrators to create custom ESXi images for different types of deployment, such as ISO-based installation, PXE-based installation, and Auto Deploy.	Nothing comparable	Nothing comparable
Auto Deploy	vSphere Auto Deploy enables faster provisioning of multiple hosts. New hosts are automatically provisioned based on rules defined by user.	Requires in-depth setup in Systems Center Configuration Manager	Nothing comparable
Management Interface Firewall	ESXi Firewall is a service-oriented and stateless firewall that protects the ESXi 5.0 management interface. Configured using the vSphere Client or at the command line with esxcli interfaces.	Nothing comparable	Nothing comparable
Enhanced Virtual Hardware	32-way virtual SMP, 1TB virtual machine RAM, Non hardware accelerated 3D graphics, USB 3.0 device support, Unified Extended Firmware Interface (UEFI).	4-way virtual SMP only, 64 GB RAM per virtual machine	8-way virtual SMP only, 32 GB RAM per virtual machine