Avago Technologies MegaRAID SATA 150-4 (523) - Manual (Page 40)

2-18 Introduction to RAID
Copyright © 2003–2006 by LSI Logic Corporation. All rights reserved.
2.5.2.5 RAID 50
RAID 50 provides the features of both RAID 0 and RAID 5. RAID 50
includes both distributed parity and disk striping across multiple arrays.
RAID 50 is best implemented on two RAID 5 disk arrays with data striped
across both disk arrays.
RAID 50 breaks up data into smaller blocks, then stripes the blocks of
data to each RAID 5 disk set. RAID 5 breaks up data into smaller blocks,
calculates parity by performing an exclusive-or on the blocks, then writes
the blocks of data and parity to each drive in the array. The size of each
block is determined by the stripe size parameter, which is set during the
creation of the RAID set.
RAID 50 can support up to 8 spans and tolerate up to 8 drive failures,
though less than total disk drive capacity is available. Though multiple
drive failures can be tolerated, only one drive failure can be tolerated in
each RAID 1 level array.
Table 2.9 provides an overview of RAID 50.
Figure 2.6 provides an example of a RAID 50 level logical drive.
Table 2.9 RAID 50 Overview
Feature Description
Uses Appropriate when used with data that requires high
reliability, high request rates, high data transfer, and medium
to large capacity.
Strong Points Provides high data throughput, data redundancy and very
good performance.
Weak Points Requires 2 to 8 times as many parity drives as RAID 5.
Drives 6 to (14 drives x the number of channels)