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Redundant Array of Independent Disks
Level : 0 1 2 3 4 5 6 7 10 53 General Info

RAID 1:
Mirroring and Duplexing

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 Diagram: Level 1

RAID Level 1 requires a minimum of 2 drives to implement

CHARACTERISTICS/
ADVANTAGES		 DISADVANTAGES
  • One Write or two Read 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 of data is necessary in case of disk failure, just a copy to the replacement disk
  • Transfer rate per block is equal to single disks
  • Simplest RAID storage subsystem design
  • Highest ECC (Error Checking/Correction) 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 USES
Applications
  • Accounting
  • Payroll
  • Financial
  • Any application requiring very high availability

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