Compaq 3200 - Manual (Page 148)

E-6 Understanding Drive Arrays
Writer: Rickard Project: Compaq Smart Array 3200 Controller Reference Guide Comments: 340862-002
File Name: L-APPE.DOC Last Saved On: 12/7/98 9:30 AM
COMPAQ CONFIDENTIAL - NEED TO KNOW REQUIRED
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 97% 67% to 97% 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 3 3 2 1
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, RAID 4 uses
the least amount of
storage capacity for
fault tolerance.
Tolerant of multiple,
simultaneous drive
failures. Higher
performance than
RAID 4 or 5. RAID 1
uses the most
storage capacity for
fault tolerance, and
requires an even
number of drives.
Best performance,
but data is lost if any
drive in the logical
drive fails. RAID 0
uses no storage
space for fault
tolerance.
*A ll drives are the same capacity.
If you require a fault-tolerant system for critical data, Compaq recommends
using RAID 5 for maximum storage space efficiency or RAID 1 if I/O
performance is more important.
If you store non-critical data, and space and performance are both important,
RAID 0 offers the best of both parameters. However, RAID 0 has no data
protection and you will have to rely on backups in the event of hardware failure.