XenDesktop 5 relies on the use of an SQL database to store “state information”: which Virtual Desktop groups are available, which Virtual Desktop Appliances are in use, and which users are using them.
Because of the real-time nature of this “state information”, it is not appropriate for updates to be lost or delayed in the event that the SQL database becomes unavailable. For this reason, some users may feel that they need a highly available SQL database to support their business needs, and HA (High Availability) can be an important requirement for these deployments.
This document explores the possibility of using Citrix XenServer and Marathon everRun MX 6.1 to support a highly available Microsoft SQL Server.
A number of tests were performed to see whether Marathon everRun MX 6.1 could support a highly available Microsoft SQL Server for use by XenDesktop 5 Service Pack 1.
These tests included setting up a constant stream of SQL traffic between a XenDesktop 5 Service Pack 1 broker, and the SQL Server. High Availability events such as loss of a host or loss of network connectivity were then induced to see if the SQL traffic could be interrupted.
The result of the tests showed that Marathon everRun MX was able to handle the High Availability events, and was able to keep the SQL Server running without service interruptions, loss of data, or loss of in-flight transactions that might have caused problems with XenDesktop 5 Service Pack 1.
Performance tests were not appropriate with the available hardware.
Marathon everRun MX 6.1 (description by Marathon Technologies)
Marathon’s everRun MX is a software product that provides zero-downtime fault tolerant protection for Windows application operating in a XenServer pool. With everRun installed, the administrator uses a wizard-based GUI to simply select and protect a VM. Once protected, everRun provides continuous, uninterrupted application availability. Unlike traditional failover technologies there is no downtime or restart of the VM required. In the event of a failure, the application automatically continues without loss of data or interruption of network sessions and all in-flight transactions are completed. everRun protects any Microsoft application without requiring scripting, modification or specialized administrative skills. In addition, everRun’s disk mirroring technology permits use of local disk storage without the requirement for costly and complex shared storage devices.
everRun operates by running redundant VM’s operating across 2 XenServer hosts. Marathon’s Lockstep technology synchronizes the redundant VM’s so they execute identically. In the event of a failure, the surviving VM simply continues to operate without interruption. When a failed component is repaired, redundancy is transparently and automatically re-established .
For full details of Marathon everRun MX see http://www.marathontechnologies.com
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