In the first part of this blog series we looked at specific details on Citrix Delivery Center and the Disaster Recovery demonstration for SAP NetWeaver. In this posting we will cover different High Availability solutions also demonstrated at SAP. In addition to this blog series, please refer the Reference Architecture document that provides all the technical details about Citrix and Marathon solutions implemented for SAP.

Getting back to High Availability, Citrix XenServer and Marathon Technologies everRun VM for XenServer provide solutions that covers a broad spectrum of High Availability requirements  ranging from maintenance to complete system-level fault tolerance. Given the breadth of High Availability solutions, IT administrators are bound to find a Citrix XenServer High Availability solution to meet their application availability needs.  

When looking for an HA solution, various factors such as application criticality and business impact must be considered before choosing a particular solution for an application. A more detailed report on determining availability requirements can be found here.  
In our Proof Of Concept environment at SAP, we showcased all levels of High Availability offered by XenServer and everRun VM. First let’s look at the out-of-the-box High Availability solutions that XenServer alone delivers:

  • XenMotion: XenMotion supports live migration of running virtual machines from one XenServer to another. The primary purpose of XenMotion is to prepare for planned server maintenance.  The end user will not experience any interruption in application performance in XenMotion.
  • XenServer High Availability (HA) – Level 1: XenServer HA provides High Availability by automatically restarting failed virtual machines on a different XenServer host within the same resource pool.  The end user will experience an interruption in service as the virtual machine restarts.

In addition, Marathon Technologies everRun VM for XenServer provides High and Continuous Availability for critical virtual machines hosting business applications like SAP NetWeaver Portal:

  • everRun VM for XenServer-- Level 2: Marathon Technologies everRun VM Level 2 delivers High Availability from component-level fault tolerance, eliminating downtime caused by I/O component failures and guaranteeing recovery from system failures. The solution identifies faulty I/O pathways before they become a problem and responds to a wide range of I/O and component failures. Active validation of all components on primary and secondary hosts ensures smooth recovery following any primary host component failure.  
  • everRun VM for XenServer – Level 3: Marathon Technologies everRun VM Level 3 provides Continuous Availability from system-level fault tolerance, eliminating data loss, downtime and transaction loss. It offers all of the benefits of Level 2 and adds two important attributes:
    a.    Zero downtime, even with complete XenServer host failure.
    b.    Preservation of application and memory states during failure.

The following video features the Marathon everRun VM Level 3 High Availability solution demonstrated at SAP Co-Innovation Labs, Palo Alto. Again, for more technical details on the implementation, please take a look at the Reference Architecture.