The Problems of Having Thousands of Databases on a Single Instance - SQL Server

Having thousands of databases on a single SQL Server instance can lead to several problems, including:

Resource contention: Each database requires its own set of resources, such as memory, disk I/O, and CPU time. With thousands of databases, these resources can quickly become scarce and lead to performance problems.

Maintenance challenges: Maintaining thousands of databases can be a daunting task, especially when it comes to tasks such as backups, restores, and monitoring. It can be difficult to keep track of which databases need maintenance and ensuring that all databases are properly maintained can become an overwhelming task.

Security risks: With thousands of databases, it can be challenging to maintain proper security protocols. Each database may have its own set of users and permissions, making it difficult to manage access and enforce security policies across all databases.

Increased risk of downtime: If one database experiences issues, it can potentially affect other databases on the same server instance. With thousands of databases, the risk of downtime can be significant, as an issue in one database can quickly snowball and affect many others.

Limited scalability: With so many databases on a single instance, scaling the system can be difficult. Adding more databases can quickly consume available resources and potentially require the addition of more hardware or instances, which can be costly and complex.

While having thousands of databases on a single SQL Server instance may seem like an attractive solution for managing large volumes of data, it can lead to a host of problems and complexities that may outweigh the benefits. It's essential to carefully consider the pros and cons before embarking on a strategy of this nature.