What is the best backup strategy for a large database supporting online sales?

The best backup strategy for a large database supporting online sales is the use of mirrored hard disks. This approach involves creating an exact copy of the data in real-time, ensuring that if the primary disk fails, the system can immediately access the mirrored disk without any loss of data or significant downtime.

For an online sales database, where availability and data integrity are critical, ensuring that the database remains operational at all times is essential. Mirroring provides high availability by protecting against hardware failures and allows for quick recovery in case of disk-related issues.

While other options, such as weekly full backups with daily incremental backups or daily full backups, can be part of a robust backup strategy, they do not offer the same immediate failover capability that mirrored disks provide. Similarly, clustered servers enhance availability through redundancy at the server level but do not specifically address real-time data protection at the disk level in the same direct way that mirrored disks do.