The Fundamental Considerations of SQL Server Disaster Recovery

• By Karen Anthony
• 14-07-2022
• Technology

Microsoft SQL Server is an extensively used relational database management system that was developed and introduced by Microsoft.

According to Wikipedia, the chief function of Microsoft SQL Server is to store and retrieve data at the request of other software applications. Disaster recovery is actually the most frequently used method utilized for SQL database safeguards. As such DBA should focus on adequate precautions to safeguard the database from any loss. Let us understand the key considerations while recovering critical SQL data from any man made or natural disaster.

Fundamental Aspects of SQL Disaster Recovery
Your SQL disaster recovery plan should be comprehensive, and it may incorporate all dependencies. If the present SQL database server requires restoration. Ensure that all SQL Server dependencies are very much in place. Windows accounts, file system dependencies, applications, and several other database server aspects should necessarily be available since all disaster recovery plans in the past have not been successful since the fundamental hardware platform dependency did not exist.

Your disaster recovery plan must be malicious and simple to the extent possible. Just a handful of SQL database disaster recovery technologies restrict the actions possible on the source database server. For instance, whether you can modify or alter the recovery model while utilizing database mirroring.

Let us learn a few additional steps for ensuring that the SQL Server disaster recovery website is updated consistently: Log shipping and replication cannot succeed in replicating logins. Moreover, several processes are necessary to allow all logins to be in a single place and make them up-to-date in the case of disaster recovery. SQL database server instances, when armed with provisions such as automated backup & recovery are not adequately secured against unexpected devastating events like ransom attacks, multi-site database failure, etc. When a thoroughly tested and documented stratagem is absent, SQL database disaster recovery may take much longer in comparison to SLAs, and recovery may fail and culminate in a prolonged outage. Let us understand the fundamental considerations while chalking a perfect SQL database recovery plan. These core considerations are based chiefly on defining precise metrics for a successful SQL recovery, opting for an effective backup stratagem, leveraging the power and versatility of SQL availability features, and more.

Defining the Key Metrics
SQL Server key metrics for disaster recovery are RPO or Recovery Point Objective and RTO or Recovery Time Objective. These metrics are integral to the SLA or Service Level Agreement.

1. RPO is supposed to be the most recent “point in time” for restoring an SQL database Server disaster recovery. RPO is dependent on the backup frequency. If backups are frequent, and so the extent of critical data loss will be reduced. RPO implies the acceptable data loss amount that your company can withstand in the event of a data loss issue. This metric is always considered with time in mind.

2. RTO is supposed to be the “maximum time allowed” for restoring the database server to normalcy post a disaster. RTO is dependent on the size and type of backup. Differential backups take lesser time for restoration than full backups.

3. RLO is Recovery Level Objective and refers to the specific level of granularity when your crucial data is recovered. It can include instance-level database level, table level or database level.

The shorter the RPO and RTO when you take time into consideration, and the finer the granularity of the RLO, the higher the expenses involved in executing a disaster stratagem. Most organizations do not enjoy an unrestricted budget. You may exercise some budgetary constraints. Always consider the storage costs, hardware costs, and even licensing expenses of the solution. If you are thinking in terms of several locations, it is essential to consider those additional expenses as well.

Opt for the Perfect Backup Stratagem
SQL database server allows several backup options to be used in combination for speeding up the entire SQL database disaster recovery process depending on the RTO while retrieving maximum data as per the RPO. Different types of backup are:

Differential Backup: Helps create a copy of every change that has taken place in the database since the last full backup. It facilitates faster restoration.

Full Backup: Helps create a copy of every transaction log and database object. It is best for recovering and restoring all items in case of database failures.

Tail-log Backup: Helps create a complete backup of all log records not backed up yet.

Leverage the Power & Versatility of Availability Features of SQL

SQL Server 2017 introduced many effective availability features for supporting disaster recovery. Moreover, SQL database server installations were extended to Linux. You need to consider these helpful features in your SQL disaster recovery plan.

Always On Availability Groups
This feature facilitates automated disaster recovery and site resilience.

FCI or Failover Cluster Instance
FCI uses the inherent clustering attribute of Windows Server for extending perfect protection to the entire SQL database server installation. It provides a proper recovery solution for SQL disaster recovery.

Log Shipping: This process helps back up automatically the transaction logs associated with the primary database. It will then carry on by copying and applying them on ‘Warm Standby.’

Conclusion
The SQL database server may encounter disasters at any time. It is the responsibility of the DBA to make perfect arrangements to combat these disasters and avoid any data loss. You should always have an effective data recovery plan.