User guide

E-6 Compaq StorageWorks RAID Array 4100 User Guide
Table E-1
RAID Level Characteristics
Distributed
Data
Guarding
(RAID 5)
Data
Guarding
(RAID 4)
Mirroring
(RAID 1)
No Fault
Tolerance
(RAID 0)
Usable Disk
Space*
67% to 93% 67% to 93% 50% 100%
Disk Space
Formula
(n = no. of
drives)
(n-1)/n (n-1)/n n/2 n
Parity and
Data
Redundancy
Parity
distributed
over each
drive
Dedicated
parity drive
Duplicate
data
None
Minimum
Number of
Drives
3321
Comments
Tolerant of
single drive
failures.
Higher
performance
than RAID 4.
Uses the
least
amount of
storage
capacity for
fault
tolerance.
Tolerant of
single drive
failures.
Like RAID 5,
uses the
least
amount of
storage
capacity for
fault
tolerance.
Tolerant of
multiple,
simultaneous
drive failures.
Higher
performance
than RAID 4 or
5. Uses the
most storage
capacity for
fault tolerance.
Requires an
even number
of drives.
Best
performance
but data is
lost if any
drive in the
logical drive
fails. Uses
no storage
space 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