//
you're reading...
Virtualization and Cloud

VMware ESX server architecture

VMware ESX Server is virtual infrastructure partitioning software designed for serve consolidation, rapid deployment of new servers, increased availability, and simplified management — helping to improve hardware utilization, save space, IT staffing and hardware costs.

Virtualization at a glance

In Figure , each VM is configured with one CPU, an allocation of memory and disk, and  two virtual Ethernet adapters. In reality, they share the same physical CPU and   access noncontiguous pages of memory. Part of the memory of one of the VMs is currently swapped to disk. Their virtual disks are files on a common file system. Each has a network interface bound to and sharing a single physical network adapter. The second network interface in each VM is bound to a virtual network interface within the ESX Server system.

Virtualization in detail

The VMware virtualization layer brings hardware virtualization, pioneered on IBM VM/370 and  other  mainframe environments, to the standard Intel server platform. The virtualization layer is common among VMware desktop and server products, providing a consistent platform for development, testing, delivery and support of application workloads from the developer desktop to the workgroup and to the data center.
As with mainframe virtualization, the VMware virtual machine offers complete hardware virtualization. The guest operating system and applications inside a VM can never directly  know which physical resources they are accessing, such as which CPU they are running on in a multiprocessor system or which physical memory is mapped to their pages. The virtualization of the CPU incorporates direct execution. The hardware CPU executes non-privileged instructions without overheads introduced by emulation.
The virtualization layer provides an idealized physical machine that is isolated from other VMs on the system. It provides the virtual devices that map to shares of specific physical devices. These devices include virtualized CPU, memory, I/O buses, network interfaces, storage adapters and devices, human interface devices, BIOS and others.
Each VM runs its own operating system and applications. They cannot talk to each other or leak data, other than through networking mechanisms similar to those used to connect separate physical machines. This isolation leads many users of VMware software to build internal firewalls or other network isolation environments, allowing some VMs to connect to the outside while others are connected only to virtual networks through other VMs.

CPU virtualization

Each virtual machine appears to run on its own CPU, or set of CPUs, fully isolated from other VMs, with its own registers, translation lookaside buffer, and other control structures. Most instructions are directly executed on the physical CPU, allowing compute-intensive workloads to run at near-native speed. Privileged instructions are performed safely by the patented and patent-pending technology in the virtualization layer.

Memory virtualization

While a contiguous memory space is visible to each VM, the physical memory allocated may not be contiguous. Instead, noncontiguous physical pages are remapped efficiently and presented to each virtual machine. Some of the physical memory of a virtual machine may in fact be mapped to shared pages, or to pages that are unmapped or swapped out. This virtual memory management is performed by ESX Server without the knowledge of the guest operating system and without interfering with its memory management subsystem.

Disk virtualization

Support of disk devices in VMware ESX Server is an example of the product’s hardware independence. Each virtual disk is presented as a SCSI drive connected to a SCSI adapter. This device is the only disk storage controller used by the guest operating system, despite the wide variety of SCSI, RAID and Fibre Channel adapters that might be used in the system. This abstraction makes VMs at once more robust and more transportable. There is no need to worry about the variety of potentially destabilizing drivers that may need to be installed on guest operating systems, and the file that encapsulates a virtual disk is identical no matter what underlying controller or disk drive is used.VMware ESX Server can be used effectively with storage area networks (SANs). ESX Server supports QLogic and Emulex host bus adapters, which allow an ESX Server computer to be connected to a SAN and to see the disk arrays on the SAN.

Network virtualization

You may define up to four virtual network cards within each VM. Each virtual network card has its own MAC address and may have its own IP address or multiple addresses as well. It  might be mapped to a dedicated network interface on the physical server, known as the Outbound Adapter, or virtual network interfaces from multiple virtual machines may be connected to a single network card. VMware ESX Server manages both the allocation of resources and the secure isolation of traffic meant for different virtual machines even when they are connected to the same physical network card. Before virtual machines defined to ESX Server can be configured to access a network, at least one virtual ethernet switch must be created within ESX Server. When two or more virtual machines are connected to the same virtual ethernet switch, network traffic between the virtual machines will be routed locally. If an outbound adapter is attached to the virtual ethernet switch, each virtual machine will also be able to access the external network through the outbound adapter.

Virtual LAN (VLAN) and port groups

An additional network option involves patching a virtual network interface to a Virtual LAN (VLAN). A  VLAN is made up of a port group created within ESX Server. Each port group is assigned a unique VLAN ID. VLANS can be used to isolate virtual machine network traffic on the ethernet virtual switch and on the external network.

VLAN connections may be used for high-speed networking between VMs, allowing private, cost-effective connections between the them. The isolation inherent in their design makes them especially useful for supporting network topologies that normally depend on the use of additional hardware to provide security and isolation

For example, an effective firewall can be constructed by configuring one virtual machine on an ESX Server system with two virtual Ethernet adapters, one bound to a VLAN connected to an outbound adapter, giving it a connection to a physical network. The other is bound to a different VLAN ID.
Other virtual machines would be connected only to the internal VLANs. By running filtering software in the dual-homed virtual machine, a user can construct an effective firewall without the need for additional hardware and with high-performance virtual networking between the virtual machines. A similar approach can be used with multitier applications, with the Web or application servers reachable from other systems but with the database server connected only to the other tiers.

Many people may have had earlier experience with VMware’s virtualization products in the form of    VMware Workstation or VMware GSX Server. As aforementioned, VMware ESX   Server is quite different to other VMware products in that it runs directly on the hardware, offering a mainframe class virtualization software platform that enables the deployment of multiple, secure, independent virtual machines on a single physical server.

VMware ESX Server allows several instances of operating systems like Windows Server  2003, Windows Server 2008, Red Hat® and (Novell®) SuSE Linux, and more, to run in  partitions independent of one another. Therefore this technology is a key software enabler for  server consolidation that provides the ability to move existing, unmodified applications and  operating system environments from a large number of older systems onto a smaller number of new high performance System x platforms.Real cost savings can be achieved by allowing for a reduction in the number of physical  systems to manage, saving floor space, rack space, reducing power consumption, and eliminating the headaches associated with    consolidating dissimilar operating systems and pplications that require their own OS instance.

Additionally, VMware ESX Server helps you build cost-effective, high-availability solutions by using failover clustering between virtual machines. Until now, system partitioning (the ability  of one server to run multiple operating systems simultaneously) has been the domain of mainframes and other large midrange servers. But with VMware ESX Server, dynamic, logical partitioning can be enabled on IBM system

VMware ESX Architecture

VMware ESX in Network Infrastructure

instead of deploying multiple servers scattered around a company and running a single application on each, they can be consolidated together physically, while enhancing system availability at the same time. VMware ESX Server allows each server to run multiple operating systems and applications in virtual machines — providing centralized IT management. Since these virtual machines are completely isolated from one another, if one were to go down, it would not affect the others.

Overview of using VMware ESX Server with SAN

A storage area network (SAN) is a highly effective means to support and provision VMware products. Consideration should be given for a SAN’s high performance characteristics and feature functions such as Flashcopy, Volumecopy, and mirroring. The configuration of a SAN requires careful consideration of  components to include host bus adapters (HBAs) in the host servers, SAN switches, storage processors, disks, and storage disk arrays. A SAN topology has at least one switch present to form a SAN fabric

Benefits of Using VMware ESX Server with SAN

Using a SAN with VMware ESX Server allows you to improve data accessibility and system
recovery:
 Effective store data redundantly and eliminate single points of failure.
 Data Centers can quickly negotiate system failures.
 VMware ESX Server systems provide multipathing by default and automatically support
virtual machines.
 Using a SAN with VMware ESX Server systems extends failure resistance to servers.Using VMware ESX Server with a SAN makes high availability and automatic load balancing affordable for more applications than if dedicated hardware is used to provide standby services:

Because shared central storage is available, building virtual machine clusters that use
MSC  becomes possible.
If virtual machines are used as standby systems for existing physical servers, shared
storage is essential and a viable solution.
VMware vMotion capabilities to migrate virtual machines seamlessly from one host to
another.
Use VMware High Availability (HA) in conjunction with a SAN for a cold standby solutions guarantees an immediate, automatic failure response.
 Use VMware Distributed Resource Scheduler (DRS) to migrate virtual machines from one host to another for load balancing.
VMware DRS clusters, put an VMware ESX Server host into maintenance mode to have the system migrate all running virtual machines to other VMware ESX Server hosts.The transportability and encapsulation of VMware virtual machines complements the shared nature of SAN storage. When virtual machines are located on SAN based storage, you can shut down a virtual machine on one server and power it up on another server or to suspend it on one server and resume operation on another server on the same network in a matter of minutes. This ability allows you to migrate computing resources while maintaining consistent shared access.

CPU virtualization

Each virtual machine appears to run on its own CPU, or set of CPUs, fully isolated from other

VMs, with its own registers, translation lookaside buffer, and other control structures. Most

instructions are directly executed on the physical CPU, allowing compute-intensive workloads

to run at near-native speed. Privileged instructions are performed safely by the patented and

patent-pending technology in the virtualization layer.

Memory virtualization

While a contiguous memory space is visible to each VM, the physical memory allocated may

not be contiguous. Instead, noncontiguous physical pages are remapped efficiently and

presented to each virtual machine. Some of the physical memory of a virtual machine may in

fact be mapped to shared pages, or to pages that are unmapped or swapped out. This virtual

memory management is performed by ESX Server without the knowledge of the guest

operating system and without interfering with its memory management subsystem.

Disk virtualization

Support of disk devices in VMware ESX Server is an example of the product’s hardware

independence. Each virtual disk is presented as a SCSI drive connected to a SCSI adapter.

This device is the only disk storage controller used by the guest operating system, despite the

wide variety of SCSI, RAID and Fibre Channel adapters that might be used in the system.

This abstraction makes VMs at once more robust and more transportable. There is no need

to worry about the variety of potentially destabilizing drivers that may need to be installed on

guest operating systems, and the file that encapsulates a virtual disk is identical no matter

what underlying controller or disk drive is used.

VMware ESX Server can be used effectively with storage area networks (SANs). ESX Server

supports QLogic and Emulex host bus adapters, which allow an ESX Server computer to be

connected to a SAN and to see the disk arrays on the SAN.

Network virtualization

You may define up to four virtual network cards within each VM. Each virtual network card

has its own MAC address and may have its own IP address or multiple addresses as well. It

might be mapped to a dedicated network interface on the physical server, known as the

Outbound Adapter, or virtual network interfaces from multiple virtual machines may be

connected to a single network card. VMware ESX Server manages both the allocation of

resources and the secure isolation of traffic meant for different virtual machines even when

they are connected to the same physical network card.

Before virtual machines defined to ESX Server can be configured to access a network, at

least one virtual ethernet switch must be created within ESX Server. When two or more virtual

machines are connected to the same virtual ethernet switch, network traffic between the

virtual machines will be routed locally. If an outbound adapter is attached to the virtual

ethernet switch, each virtual machine will also be able to access the external network through

the outbound adapter.

Advertisements

Discussion

No comments yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: