Raid 5 And Raid 5+Hot Spare - easyRAID S4-ESTT User Manual

User's Manual

RAID 5 and RAID 5+hot spare

RAID 5 uses a mathematical expression that compares data from three drives and
calculates a fourth piece of data called "parity" which is saved on a fourth drive. 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. RAID
5 requires at least three drives. The allows users to set RAID 5 with three drives and the
fourth drive as a "hot spare" ready to be used for rebuilding data in case one of the other
drives fails. This is RAID 5 +hot spare function.
RAID 5: Independent data disks with distributed parity blocks
Characteristics:
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)
In RAID 5, installed drives each are 40 GB, 50
GB, 60 GB, 70 GB, the RAID capacity will be 120
GB.
In RAID 5 + hot spare, installed 40 GB, 50 GB, 60
GB each in disk 2, 3, 4 and installed 70 GB in disk
1 as hot spare disk, the RAID capacity will be 80
GB.
Recommended use:
File and application servers
Database servers
WWW, E-mail and News
servers
Intranet servers
Most versatile Raid level
- 2-6 -