Selecting a RAID Level

Level

Description and

Pros

Cons

Maximum

Fault

 

Use

 

 

Physical

Tolerant

 

 

 

 

Drives

 

0

Data divided in

High data

No fault

One to 15

No

 

blocks and

throughput

tolerance. All

 

 

 

distributed

for large

data lost if

 

 

 

sequentially (pure

files

any drive

 

 

 

striping). Use for

 

fails.

 

 

 

non-critical data

 

 

 

 

 

that requires high

 

 

 

 

 

performance.

 

 

 

 

1

Data duplicated on

100% data

Doubles disk

2

Yes

 

another disk

redundancy

space.

 

 

 

(mirroring). Use

 

Reduced

 

 

 

for read-intensive

 

performance

 

 

 

fault-tolerant

 

during

 

 

 

systems.

 

rebuilds.

 

 

3

Disk striping with a

Achieves

Performance

Three to 15

Yes

 

dedicated parity

data

not as good as

 

 

 

drive. Use for non-

redundancy

RAID 1

 

 

 

interactive apps

at low cost

 

 

 

 

that process large

 

 

 

 

 

files sequentially.

 

 

 

 

5

Disk striping and

Achieves

Performance

Three to 15

Yes

 

parity data across

data

not as good as

 

 

 

all drives. Use for

redundancy

RAID 1

 

 

 

high read volume

at low cost

 

 

 

 

but low write

 

 

 

 

 

volume, such as

 

 

 

 

 

transaction

 

 

 

 

 

processing.

 

 

 

 

10

Data striping and

High data

More

Four to 14

Yes

 

mirrored drives.

transfers,

complicated

(must be a

 

 

 

complete

 

multiple of

 

 

 

redundancy

 

two)

 

30

Disk striping with a

High data

More

Six to15

Yes

 

dedicated parity

transfers,

complicated

 

 

 

drive.

redundancy

 

 

 

50

Disk striping and

High data

More

Six to 15

Yes

 

parity data across

transfers,

complicated

 

 

 

all drives.

redundancy

 

 

 

Note: The maximum number of physical drives supported by the Express 500 controller is 15.

18MegaRAID Express 500 Hardware Guide