| RAID Level: |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
10 |
53 |
0+1 |
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 Level 1 requires a minimum of 2 drives to implement |
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 |
Disadvantages 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" |