easyRAID S8A2, User Manual

Page: 58 / 60

RAIDGuard X User’s Manual
54
RAID 5
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. Data on RAID 5 is block-
interleaved.
RAID 5: Independent data disks with distributed parity blocks
Characteristics: Recommended use:
„ Each entire data block is written on a data disk.
Parity for blocks in the same rank is generated
on Writes, recorded in a distributed location and
checked on Reads.
„ Highest Read data transaction, medium Write
data transaction rate.
„ Relatively low ratio of ECC (Parity) disks to data
disks means high efficiency (compared to other
RAID levels).
„ Good aggregate transfer rate.
„ Storage capacity = (No. of disks – 1) × (capacity
of smallest disk)
„ File and application
servers
„ Database servers
„ WWW, E-mail and News
servers
„ Intranet servers
„ Most versatile RAID level
The diagram below represents the writing of data on a RAID 5 array composed of four
HDDS connected to the controller. Parity blocks are represented by the letter P.
Arrangement of data and parity blocks saved on a Level 5 RAID