In this article we take an in-depth look into SQL Server clusters and learn how they can prove beneficial to an organization.
Clustering in SQL Server refers to the installation of multiple instances of SQL Server into one or more physical servers, preferably ones running on Microsoft Windows. This is done to add on to the availability of the database, as a clustered SQL Server database will be available across the clustered servers at all times. So in case either of the server crashes, the database can still be accessed through other clustered servers. The clustering service in SQL Server is available in its editions of 2005 and beyond.
Windows failover cluster usually uses a shared storage space, mostly a Shared Area Network (SAN). After you install a SQL Server to the windows failover cluster you should have the databases and the system on a same storage, so that the database can be accessed from any of the clustered servers. Although there is only a single instance of the database, you can however request the network name and SQL Server instance from any of the cluster node/ clustered server.
In case of a crash in one of the servers in failover cluster service, the data on the crashed server automatically moves to another server on the same storage, and the ongoing operations are rolled back. Hence the original database remains and can still be accessed from another node/server. And once the crashed server is accessed again, you can resume operations from where you left.
Failover Cluster Server can make your work easier in server ways
- In case of a standalone server, a crash is a nightmare, as you will not have any option but to wait till the server is back online. Whereas in case of failover cluster service you can switch to another server and resume operations.
- Another problem with standalone servers comes while applying security patches, the server needs to be offline while rebooting whereas in failover clusters, you can just switch to another node till the patch is applied to the node.
- Using failover clusters also provides you with an additional troubleshooting tool in the tool kit.
- Clustering supports a lot of SQL operations which are not very well supported with other alternatives. With cluster service, database, logins, job alerts etc all comes together in the form of a single unit.
Misunderstandings related to cluster service that one needs to steer clear off
- Cluster service cannot be used to get better performance out of SQL Server, for that you will need a powerful server and a faster storage.
- Clustering does not mean everything in SAN is redundant, storage and database both will go offline together.
- Clustering does not mean easier or safer backups, regular maintenance should be continued.
Cluster service is not full proof, it also has its own set of drawbacks, but it is a feature that can help you access your database at all times
Even with failover clusters chances of data loss remains in the event of a SQL crash
In many mid to small sized firms, failover cluster implementation is far from what is ideally expected. Thus chances of data loss in the event of a SQL crash remains. To assuredly get back all their data, such firms can look to a sql recovery tool like DataNumen SQL Recovery. This powerful software can pry out every piece of data stored in the SQL database file with ease. Further the software is capable of even bringing back records that users may have deleted by mistake.
Alan Chen is President & Chairman of DataNumen, Inc., which is the world leader in data recovery technologies, including access recovery and sql recovery software products. For more information visit https://www.datanumen.com/