RAID LEVEL 1: Mirroring & Duplexing
0 1 2 3 4 5 6 10 50 0+1
RAID LEVEL 1: Mirroring & Duplexing
0 1 2 3 4 5 6 10 50 0+1

Click on the diagram to see Raid 1 in action

For Highest performance, the controller must be able to perform two concurrent separate Reads per mirrored pair or two duplicate Writes per mirrored pair.

RAID Level 1 requires a minimum of 2 drives to implement

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Characteristics & Advantages

  • One Write or two Reads possible per mirrored pair
  • Twice the Read transaction rate of single disks, same Write transaction rate as single disks
  • 100% redundancy of data means no rebuild is necessary in case of a disk failure, just a copy to the replacement disk
  • Transfer rate per block is equal to that of a single disk
  • Under certain circumstances, RAID 1 can sustain multiple simultaneous drive failures
  • Simplest RAID storage subsystem design


  • Highest disk overhead of all RAID types (100%) - inefficient
  • Typically the RAID function is done by system software, loading the CPU/Server and possibly degrading throughput at high activity levels. Hardware implementation is strongly recommended
  • May not support hot swap of failed disk when implemented in "software"

Recommended Applications

  • Accounting
  • Payroll
  • Financial
  • Any application requiring very high availability