RAID-1 is shorthand for RAID Level 1: Mirroring and Duplexing.

RAID Level 1 is a type of RAID configuration which uses 2 disks to provide 100% redundancy in case of a single drive failure.


  • Availability: Can tolerate the loss of 1 drive
  • Capacity: 50% (2 drives = 1 drive available space)
  • Degradation: Slight degradation of read performance during rebuild, write speed actually increases. Rebuilding is fast.
  • Performance: Reads are up to twice as fast as a single disk, writes are the same as the speed of a write to the slowest of the 2 disks.
  • Summary: Highest fault tolerance / availability, lowest storage capacity
  • Typical Uses: Accounting, payroll, financial services, databases servers, highly available services

How it works

  • READ: read data from both disks at the same time
  • WRITE: write data to both disks, write is complete when both disk writes complete (when writing in synchronous mode)

Comparison with other RAID types:

  • RAID-0 has faster writes and equal reads (for a 2-drive RAID-0 set)
  • RAID-5 has slower writes and faster reads (as it requires minimum 3 disks, but can read from all 3)

More Information

metawerx specific

referring pages