Compaq RAID Array 4100 User Manual page 132

E-6 Compaq StorageWorks RAID Array 4100 User Guide
Distributed
Guarding
(RAID 5)
67% to 93%
Usable Disk
Space*
Disk Space
Formula
(n = no. of
drives)
Parity and
distributed
Data
over each
Redundancy
Minimum
Number of
Drives
Tolerant of
Comments
single drive
failures.
Higher
performance
than RAID 4.
Uses the
least
amount of
storage
capacity for
fault
tolerance.
* All drives are the same capacity
If you require a fault-tolerant system for critical data, use RAID 5 for
maximum storage space efficiency. Use RAID 1 if I/O performance is more
important.
If you will be storing non-critical data, and space and performance are both
important, RAID 0 offers the best of both parameters. However, RAID 0 has
Table E-1
RAID Level Characteristics
Data
Data Guarding
(RAID 4)
67% to 93%
(n-1)/n (n-1)/n
Parity Dedicated
parity drive
drive
3 3
Tolerant of
single drive
failures.
Like RAID 5,
uses the
least
amount of
storage
capacity for
fault
tolerance.
Mirroring No Fault
(RAID 1) Tolerance
(RAID 0)
50% 100%
n/2 n
Duplicate None
data
2 1
Tolerant of Best
multiple, performance
simultaneous but data is
drive failures. lost if any
Higher drive in the
performance logical drive
than RAID 4 or fails. Uses
5. Uses the no storage
most storage space for
capacity for fault
fault tolerance. tolerance.
Requires an
even number
of drives.