Administrator Guide

Table 2. RAID level comparison (continued)
RAID level Min. disks Description Strengths Weaknesses
performance; protects
against single disk failure
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
performance is slower
than RAID 5
10
(1+0)
4 Stripes data across
multiple RAID-1
subgroups
Highest performance and
data protection (protects
against multiple disk
failures)
High redundancy cost
overhead: because all
data is duplicated, twice
the storage capacity is
required; requires
minimum of four disks
50
(5+0)
6 Stripes data across
multiple RAID-5 sub-
groups
Better random read and
write performance and
data protection than
RAID 5; supports more
disks than RAID 5;
protects against multiple
disk failures
Lower storage capacity
than RAID 5
ADAPT 12 Distributed erasure
coding with dual disk
failure protection
Very fast rebuilds, no
spare disks (built in spare
capacity), large storage
pools, simplified initial
deployment and
expansion
Requires minimum of 12
disks
Table 3. Number of disks per RAID level to optimize virtual disk group performance
RAID level Number of disks (data and parity)
1 2 total (no parity)
5 3 total (2 data disks, 1 parity disk); 5 total (4 data disks, 1 parity
disk); 9 total (8 data disks, 1 parity disk)
Getting started 17