ESX High Availability (HA)
High Availability (HA), is a relatively new capability within VMware Infrastructure 3 and is pivotal in eliminating a single point of failure for a mission critical application. When an ESX host goes down (represented by the RED X), the virtual machines running on the failed host, migrate over to the other, healthy ESX hosts with spare capacity. After migration, the virtual machines are restarted automatically and without intervention from the systems administrator.
The advantage of high availability from a business perspective depends on the loss incurred when the server is down. If the average loss per day is $2,000, then being down for two days will have a cost of $4,000. However, high availability also has a cost associated with it that is approximately 20% more than the cost of a fully dedicated server. If a fully dedicated server is $100 per month and high availability costs $20 extra per month, then HA costs $240 for the year, which is far less than the $4,000 cost of being down for two days.
VMware HA is a leader in the industry and has created an elegant solution to solve the problem of failover at an affordable price. Typically, failover infrastructure is built on complex clustering solutions using expensive hardware. And due to the high price, the traditional solutions is available only to a small percentage of large corporations. VMware HA has implemented an innovative approach that accomplishes the same goal of failover at a reasonable cost, allowing the majority of businesses to take benefit from failover safety and high availability.
At the center of HA is the concept of separating the hardware from the application and OS. By creating a cluster of ESX hosts, the resources of each server is combined to form a resource pool. Virtual machines are created within the cluster where the hardware is separated from the guest OS by a layer of abstraction handled by the Hypervisor.
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Image depicting the sharing of resources of a
single ESX server between two Virtual Machines
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VMware HA deployed on clusters and resource pools provide a robust platform to host your business applications. VMware HA integrates with VMotion, VirtualCenter, and DRS to simplify provisioning of virtual machines, load balancing, resource allocation, and migration, while also providing a cost-effective, easy-to-use, failover solution for business applications running on virtual machines. Using VMware Infrastructure together with HA mitigate single points of failure for critical business applications running in a virtual environment. Virtualization itself provides an avenue for higher system utilization, a reduction of IT costs to reach business goals and priorities, and simplified administration of IT infrastructure.
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