Hello,
We currently have one instance of SQL2k5 SP1. We have a couple of publications, and 30 subscribers, on the instance and are considering going to either a cluster environment or db mirroring. Currently our instance seems to be busy and I am wondering if clustering really gives it a performance boost. What are your thoughts/suggestions on going to a cluster environment versus just db mirroring? Can mirroring be used for real-time failover as we need to add that as well? Thanks in advance.
John
Fail-over clustering and database mirroring are both high availability solutions that don't have any direct effect on performance. Fail-over clustering relies on shared external storage between the nodes (which is a potential single point of failure), and requires higher-end hardware in most cases. It works at the instance level. Failing over a node in the cluster typically takes 1-2 minutes on a large, active database instance.
Database mirroring works at the database level(not the instance level). There are two copies of the data (one on the Principle and one on the Mirror), so you need twice the storage space. Only the Principal database is available to service clients. If you want automatic fail-over with DB Mirroring, you need a Witness Server. You have to be running in Synchronous mode with Saftey turned on to get automatic fail-over with DB Mirroring. Database fail-over with mirroring is more like 10-15 seconds.
If you are doing Replication, it will might be easier to do fail-over clustering.
|||here are some resources that may be helpful in your decision-making:
Failover Clustering white paper:
http://www.microsoft.com/downloads/details.aspx?FamilyID=818234dc-a17b-4f09-b282-c6830fead499&DisplayLang=en
Database Mirroring:
http://www.microsoft.com/technet/prodtechnol/sql/2005/dbmirror.mspx
http://www.microsoft.com/technet/prodtechnol/sql/2005/dbmirfaq.mspx
http://www.microsoft.com/technet/prodtechnol/sql/2005/technologies/dbm_best_pract.mspx
SQL Server 2005 High Availability Resources:
http://www.microsoft.com/technet/prodtechnol/sql/themes/high-availability.mspx
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