Upon completion of this module, you should be able to:
Describe problems associated with managing large numbers of disks
List requirements and techniques for managing large amount of data
Describe commonly implemented RAID levels
Describe a performance of reliability consideration relevant to each RAID implementation
List guidelines for choosing an optimized stripe width for sequential and random I/O
RAID Technology Overview
RAID is an acronym for redundant array of inexpensive disks. The SSVM application supports the following RAID levels:
RAID 0:Striping/Concatenation
RAID 1:Mirroring
RAID 0+1:Striping plus Mirroring
RAID 5:Striping with distributed parity
Striping and Mirroring-RAID 0+1
Combining striping with mirroring can privide multiple gains including:
Significant performance inceases
Complete data redundancy
Transparent disk drive failures
Mirroring and Striping-RAID 1+0
Significant performance increases
Complete data redundancy
Transparent disk drive failures
Higher disk failure tolerance than RAID 0+1
RAID 5 limitations:
A minimum of three disks are required to implement RAID 5 in Volume Manager
RAID 5 cannot be mirrored, reduncancy is provided through the parity information
Write-intensive performance can be poor
If there are more than 20 percent writes, an alternative RAID option, such as RAID 0+1,should be considered
There can be severe performance degradation with a failed disk in a write-intensive environment
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