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Another option that can be leveraged in a multisystem environment is cross-site mirroring or XSM. XSM provides a method of copying or duplicating the data in an independent ASP to a second system which could optionally be geographically separated. We use cross-site mirroring in our sample scenario.
XSM uses a direct connection to the mirror system to write all changes to memory pages onto both systems in order to maintain data synchronization. When configuring cross-site mirroring you define logically equivalent independent ASPs on both systems. Then, when you start mirroring, XSM first copies all data from the designated primary copy to the mirror copy. When synchronized, each change to a page in memory on the primary will also be changed on the backup. Cluster Services can then provide failover support allowing you to switch to the backup system in a defined resource group in the event of a hardware failure or even environmental disaster.
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When mirroring is started, the IASP on the backup is in a varied on but not available state, which allows synchronization but does not allow use of or access to the data on the mirror copy. Use of the mirror copy requires a detach from mirroring and involves a full re-synchronization in order to resume. |
