RAID 1, also known as disk mirroring, is a configuration that duplicates data across two or more physical drives. It provides high data redundancy by ensuring that every block of data is written to at least two locations simultaneously. If one drive fails, the system continues to operate using the remaining functional drive without downtime.
The write performance is equivalent to that of a single drive because the controller must commit data to all disks in the set. However, read performance can be significantly improved as the controller can retrieve different blocks of data from multiple disks at once, effectively doubling the read IOPS in a two-disk setup.
This level is typically used for operating system partitions, small databases, and critical applications where data integrity is more important than storage efficiency. RAID 1 is favored for its simplicity in recovery: since data is not striped or parity-calculated, it can be read by any standard controller if the original hardware fails.
Technical Details
- Storage efficiency is 50% when using two drives (100% capacity overhead).
- Fault tolerance: the array survives as long as at least one drive remains operational.
- Minimum drive requirement: 2 units (the capacity of the smallest drive determines total volume).