Raid 5 - Kontron Kiss-Stor 0/5 User Manual

Introduction to RAID Levels

RAID 5

RAID Level 5 requires a minimum of three drives and offers high I/O transaction
rates. RAID 5 are the ideal choice when used with on-line transaction processing
applications, such as those used in banks, insurance companies, hospitals, and
all manner of office environments. These applications typically perform large
numbers of concurrent requests, each of which makes a small number of disk
accesses.
If one drive in a RAID 5 array fails, the lost data can be rebuilt from data on the
functioning disks.
RAID 5 uses a mathematical expression that compares data from two drives and
calculates a third piece of data called "parity". Should one of the drives fail, parity
data can be used to rebuild the failed data. Under RAID 5, parity data is stored
across all drives in the array. This maximizes the amount of storage capacity
available from all drives in the array while still providing data redundancy.
Storage capacity is determined by the smallest drive in the array. That capacity is
then applied to format all other drives in the array.
If using a 40 GB, 60 GB, and 50 GB drive in a RAID 5 array, your system will see
one huge drive of 80 GB [2 (3disks-1disk) × 40 = 80].
Fig. 2: Example for RAID 5 array with three hard disks
14 KISS-Stor 0/5 – User's Manual