What is SQL?
The term SQL stands for ‘Structured Query Language’, a domain-specific language used in data management. The language is used in relational database management systems due to its advantages in handling structured data and ability to incorporate relations among data.
What is a relational database?
A relational database organises data in tables, and has the ability to handle complex relationships between different data points. Data is sorted into columns and rows, with a unique key identifying each row. Rows in the table can be linked to rows in other tables using these keys, allowing the relationships between sets of data to be tracked. Relational databases can use SQL to query and update the database.
Many businesses use SQL-based relational databases to store large records of information, so availability and data backup is vital.
What is SQL server replication?
SQL server replication is a method for duplicating and sharing data (and database objects) across multiple databases and servers. A single set of data stored in a SQL database is copied to a secondary server in a process known as master-slave replication. Any updates to the master database are made simultaneously to the additional server, aiming to enhance performance and preserve consistency.
This master-slave replication is a typical setup, but businesses can also employ master-master replication, which enables data to be copied from either server to the other. As SQL reads or writes can be performed from either server, access to data is more manageable and the possibility of data loss is greatly reduced.
Why use SQL server replication?
SQL server replication offers high availability by distributing data and objects from one database to another. There are several types of replication which can be used, including snapshot replication, transactional replication, and merge replication. Replication is usually used by mobile applications or server apps that are distributed and might have conflicts in their data.
SQL server replication is beneficial in a number of instances, for example, in data analysis where reports can be run on slave servers so the master database won’t be slowed down or corrupted. Data replication from single servers that are under large loads also supports scalability, increasing capacity and ensuring the speed of the master database is not affected.
SQL replication can also be replicated across different geographic locations. This provides an ideal solution for international businesses and increases the overall performance of the master database.
What is SQL server clustering?
SQL server clustering, also known as database clustering, is a high-availability solution where multiple SQL server instances (or nodes) are connected in a cluster, with access to a SAN (Storage Area Network) for shared storage.The SQL server data can be accessed from any instance, so if one node has an issue, you can seamlessly switch to a different node on the cluster.
Why use SQL server clustering?
When you are storing and processing critical data on your database, an interruption in access could cause significant issues. While you can take precautions to limit the risk of downtime, any infrastructure is liable to server or hardware faults or failures, which is where disaster recovery planning is essential. As a high availability solution, SQL server clustering ensures uninterrupted access to your data – in the instance of any issue with a server instance, another instance can take over.
Clustering is also beneficial for planned downtime of a node, for example if you wanted to run a security patch on one server instance, another node on the cluster can be used to avoid overall disruption of operations.
SQL server clustering additionally supports load balancing. If one server instance is under a heavy strain, another instance can take over some of the traffic, optimising the performance of the nodes.
Replication vs clustering
Both SQL server replication and clustering support high availability and disaster recovery in distinct ways. As a simplified explanation, replication backs up data across multiple databases and servers, whereas clustering connects multiple server instances with shared memory. Replication allows for data to be backed up and protected, and supports scalability and performance improvements, while clustering improves fault tolerance, allowing for seamless switching between server instances in the event of planned or unplanned downtime.
For important or high transaction applications we recommend a mixture of SQL server replication and clustering. This will give you complete automatic fail-over of databases as well as load balancing of transactions across multiple databases.
Best practices for SQL server replication and clustering
Both SQL server replication and clustering can be highly effective techniques when correctly implemented. There are several key points you should consider to ensure a resilient, high-performing setup:
- Plan for failover and disaster recovery – Designing your replication or clustering strategy with clear failover and disaster recovery procedures in mind ensures that, in the case of an incident, your plan can be immediately implemented to mitigate any impact.
- Monitor performance and replication latency – Configure monitoring tools to track latency, subscription health, agent failures, node health, quorum status and network reliability as needed. You can use the data from this monitoring to flag any potential issues and make ongoing optimisations.
- Secure communication between nodes – Implement SSL/TLS encryption to secure replication traffic, and configure firewall rules to restrict communication to trusted ISPs. Ensure your access permissions are regularly audited, and establish strong authentication protocols to protect against unauthorised access.
- Keep software and configurations consistent – Ensure all nodes in a cluster or replication technology run the same SQL server version and patch level, and use identical database collation settings, scheme versions and configurations to avoid inconsistencies.
- Automate backups and document your topology – Maintain regular backups of all involved databases, and keep records of your entire replication/clustering topology, including roles, failover procedures, and maintenance tasks
These best practices are essential to optimise SQL server replication and clustering, and ensure your infrastructure is secure. If you do not have the technical knowledge in-house to implement these best practices, an expert third-party provider can support you.
SQL server hosting with Hyve
Our flexible solutions allow you to connect SQL servers to hosted websites or to run intensive queries, manipulate data and set access controls. Whether you prefer to use MS SQL, MySQL, MariaDB, or any other SQL database, we can host and manage your infrastructure with top-of-the-line hardware, and 24/7/365 support and monitoring. Find out how our SQL hosting could benefit your business.
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