By: Ryan Watson
Have you ever felt the need to have redundancy or maybe even a failover solution for your SQL Server database?
If yes, perhaps you should look for a SQL Server Clustering or a SQL Server Mirroring solution. I have come across many users who need a disaster recovery solution for their web application. One of those users has a system which runs on Microsoft ASP.NET with a MS SQL back-end. He was suggested the possibility of MS-SQL mirroring by a web hosting provider. According to the web host this solution is a very good for applications which require very small changes to the application itself and require the minimum amount of hardware and additional software.
These servers also share a common Virtual IP address for the SQL server and the IP will be assigned to the node that is running the SQL service and the same IP should be used in the scripts to connect the SQL server.
These servers will also use the internal vLAN to check the availability of each not in the cluster with the Heart Beat Method.
A quick overview of the suggested SQL Clustering service is as follows:
- You require 2 dedicated servers, a primary database server and a secondary database server with a SAN device (Storage Area Network).
- The setup require SQL Server Enterprise Edition for the primary and secondary database servers.
- Cluster Service acts as a back-end solution which provides high availability for applications such as databases. Both servers in the cluster remain in constant communication.
- Both SQL Servers share a common storage space on a SAN device attached using iSCSI cards. SAN stores the SQL server files as well as the databases.
- The network drive on SAN device is available on the primary database server only. If the primary database server goes down for any reason the secondary server in the cluster will take over the SQL service along with the network drive causing no down time. This process is known as ‘failover’
- In this cluster, the secondary server remains inactive as an SQL server unless it is required to act as a primary database server.
- When both the servers are connected in a cluster together, they appear as a single computer to clients.
It all depends on how important the availability of your website / application is. If you require absolutely no downtime, then this kind of mirroring solution that would be suitable for your needs.
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