Administrator Guide

Table Of Contents
Table 1. Example applications and RAID levels (continued)
Application RAID level
Fast temporary storage or scratch disks for graphics, page
layout, and image rendering
0
Workgroup servers 1 or 10
Video editing and production 3
Network operating system, databases, high availability
applications, workgroup servers
5
Very large databases, web server, video on demand 50
Mission-critical environments that demand high availability and
use large sequential workloads
6
Environments that need flexible storage and fast rebuilds ADAPT
Table 2. RAID level comparison
RAID level Min. disks Description Strengths Weaknesses
NRAID 1 Non-RAID, nonstriped
mapping to a single disk
Ability to use a single
disk to store additional
data
Not protected, lower
performance (not
striped)
0 2 Data striping without
redundancy
Highest performance No data protection: if
one disk fails all data is
lost
1 2 Disk mirroring Very high performance
and data protection;
minimal penalty on
write performance;
protects against single
disk failure
High redundancy cost
overhead: because all
data is duplicated,
twice the storage
capacity is required
3 3 Block-level data striping
with dedicated parity
disk
Excellent performance
for large, sequential
data requests (fast
read); protects against
single disk failure
Not well-suited for
transaction-oriented
network applications;
write performance is
lower on short writes
(less than 1 stripe)
5 3 Block-level data striping
with distributed parity
Best cost/performance
for transaction-oriented
networks; very high
performance and data
protection; supports
multiple simultaneous
reads and writes; can
also be optimized
for large, sequential
requests; protects
against single disk
failure
Write performance is
slower than RAID 0 or
RAID 1
6 4 Block-level data striping
with double distributed
parity
Best suited for large
sequential workloads;
non-sequential read
and sequential read/
write performance is
comparable to RAID 5;
protects against dual
disk failure
Higher redundancy cost
than RAID 5 because
the parity overhead is
twice that of RAID
5; not well-suited
for transaction-oriented
network applications;
non-sequential write
Getting started 17