Additional High Availability Solutions
High availability of the system can also be achieved by using the following common, standard methods:
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Virtual Machines: Virtual machine products (such as VMWare), can provide high availability solutions that are transparent to the system, providing high availability of all system components. The Virtual Machines solution is similar to the Windows and SQL clustering solution (see Database High Availability solutions), where the system has redundant servers in an active/passive configuration. The virtual machine files are stored on a shared storage server, which is available to both the active and passive servers.
When the active server fails, the system automatically performs the failover process, activating the passive (or standby) server, which means the virtual machines are being executed on the standby server instead of the primary server. This solution can be combined with other solutions as well. For example, it can include multiple application servers accessed through a load balancer, and if one of them fails, an additional server is activated automatically by the virtual environment.
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Boot from SAN: Booting servers from a Storage Area Network (SAN) eliminates the need for each server to have its own internal disk. Server storage, including operating system files, can be relocated to a shared network disks location, and the risk of local disk failure is removed. In this scenario, the standby server is shut down and only booted up when the primary server fails.
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Network Solutions: Customers can choose any network high availability solution, as long as networking requirements, such as bandwidth and latency, are met. Network high availability is the responsibility of the customer.