Avago Technologies MegaRAID Fast Path Software - Manual (Page 34)

Page 34 LSI Corporation Confidential | July 2011
MegaRAID SAS Software User Guide Chapter 2: Introduction to RAID | RAID Levels
Figure 7: RAID 0 Drive Group Example with Two Drives
2.5.4 RAID 1 In RAID 1, the RAID controller duplicates all data from one drive to a second drive in the
drive group. RAID 1 supports an even number of drives from 2 through 32 in a single
span. RAID 1 provides complete data redundancy, but at the cost of doubling the
required data storage capacity.
Table 8 provides an overview of RAID 1. Figure 8
provides a graphic example of a RAID 1 drive group.
Figure 8: RAID 1 Drive Group
2.5.5 RAID 5 RAID 5 includes disk striping at the block level and parity. Parity is the data’s property of
being odd or even, and parity checking is used to detect errors in the data. In RAID 5,
the parity information is written to all drives. RAID 5 is best suited for networks that
perform a lot of small input/output (I/O) transactions simultaneously.
RAID 5 addresses the bottleneck issue for random I/O operations. Because each drive
contains both data and parity, numerous writes can take place concurrently.
Segment 1
Segment 3
Segment 5
Segment 2
Segment 4
Segment 6
Segment 7 Segment 8
Table 8: RAID 1 Overview
Uses Use RAID 1 for small databases or any other environment that requires fault
tolerance but small capacity.
Strong points Provides complete data redundancy. RAID 1 is ideal for any application that
requires fault tolerance and minimal capacity.
Weak points Requires twice as many drives. Performance is impaired during drive
rebuilds.
Drives 2 through 32 (must be an even number of drives)
Segment 1
Segment 1
Duplicate
Segment 2
Segment 3
Duplicate Segment 4
Duplicate
Segment 3 Segment 4
Segment 5
Segment 6
Segment 7 Segment 8
Segment 5
Duplicate Segment 6
Duplicate Segment 7
Duplicate Segment 8
Duplicate
Segment 2
Duplicate
... ... ... ...
RAID1 RAID1 RAID1 RAID1