RAID and Subsystem Architectures RAID Configurations
RAID 1 – Mirrored Disk
Unused space
File 3 File 2 File 1
Reliability Read Performance
Write Performance
Block B1 Block B2 Block C1
Block A3 Block A2 Block A1
=
Block C1 Block B2 Block B1
Block A3 Block A2 Block A1
RAID 1 (mirroring): Uses pairs of drives to create two copies of each block of data Provides very good fault-tolerance Read performance can be slightly better because drives can cooperate to read different “pieces” of the data Write performance can be slightly degraded because both drives must write a copy of the data Using duplexed controllers with one disk on each controller eliminates write performance hit Highest cost due to inefficiency in use of disk space (50%)