Specifications

Chapter #11 - Appendix - Disk Array RAID Concepts 264 000001628
MaxAttach NAS 6000 Administration Guide
Chapter #11 - Appendix - Disk Array RAID Concepts
RAID Functional Comparison
11/07/01 -- Revision 2.0.03A
RAID Functional Comparison
The table below summarizes the strengths and limitations of each RAID and JOBD
configuration.
RAID 5 Striping and parity distributed across ALL disks
YES YES
Volume Set No Striping No Parity
NO NO
Table #2 - RAID Level Comparison
RAID
Level
Description
Data
Reliability
Data Transfer and
I/O Request Rate
Application
Strength
Cost
RAID 1 All data copied onto 2
separate disks
Very high.
Can withstand
selective multiple
disk failures
Data transfer rate is higher than
single disk for reads, but does
not offer load balancing. Twice
that of a single disk for reads.
Slightly slower than single disk
for writes
General Very high.
Requires twice
as many disks
for redundancy
RAID 2 Data striped across
multiple disks with parity
on multiple disks
Very high.
Can withstand
selective multiple
disk failures
High if error correcting codes are
computed by hardware Similar
to twice that of a single disk
General High. Requires
multiple disks
for redundancy
RAID 3 Data striped across all
data disks with
dedicated parity disk
Much higher than
single disk.Can
withstand single
disk failure
Highest of all types listed here
for reading and writing Faster
than a single disk, owing to
parallel disk accesses
Video, prepress,
medical imaging,
and other large file
applications
Low. Requires
only one disk
for redundancy
RAID 4 Data striped across
some data disks with
dedicated parity disk
Much higher than
single disk.
Can withstand
single disk failure
High compared to single disk for
reads but significantly lower than
single disk for writes*.
Predominantly
read-oriented with
few writes
Low.
RAID 5 Data and parity striped
across multiple disks
Much higher than
single disk.
Can withstand
single disk failure
High compared to single disk for
read but generally lower than
single disk for writes*
Transaction processing with high
read to write ratio.
Low. Requires only
one disk for
redundancy
*Write operations are slow in these cases because the controller must read parity information from a disk and recompute parity
information for the disk before it writes information to the disk array
Table #1 - RAID Comparison
RAID Level Description
I/O
Advantage
Fault
Tol e ran c e