Technical information

About This DIGITAL HiTest Suite
HiTest Notes for Lotus Domino Windows NT Prioris MX
2–5
RAID
Level
Description Advantages/Disadvantages
3 • Parallel access array
• Small minimum chunk size
• Check bit calculated from
data
• Parity bits on dedicated disk,
data striped across remaining
disks
+ good performance in reads due to parallelism
(like RAID 0)
+ costs only slightly increased compared to
disks without high availability solutions
+ good performance with long records (high
data transfer rate)
- write performance penalty due to check bit
calculation
- cannot overlap I/O (low I/O request rate)
4 • Independent access array
• Parity disk
+ processes multiple requests simultaneously
- parity disk is a bottleneck on writes
5 • Independent access array
• Parity Bit
• Check bit and data distributed
(striped) across multiple disks
• Best in environments that are
mostly read and are not
performance sensitive
+ good performance in reads due to parallelism
(like RAID 0)
+ costs only slightly increased compared to
disks without high availability solutions
+ overlapped I/O
- write performance penalty due to check bit
calculation
1+5 • RAID 5 combined with
mirroring
• Mirroring provided by LSM
or Volume Shadowing
• Most reliable and highest
performance solution
+ good performance in reads due to parallelism
(like RAID 0)
+ double redundancy makes disk failure barely
noticeable
- spindle costs more than double
- write performance penalty due to check bit
calculation
Adaptive
3/5
• The best features of 3 and 5
• Adapts between Level 3 and
Level 5 in response to
changes in the application's
workload
+ good performance in reads due to parallelism
(like RAID 0)
+ costs only slightly increased compared to
disks without high availability solutions
+ performs well with a wide variety of I/O loads
even when load characteristics change minute
by minute.
- write performance penalty due to check bit
calculation
Installability
Installability is the ease with which hardware and software components can be installed and
configured for use. Factors that are considered when evaluating installability include clarity
of installation steps, number of steps and duration appropriate to the complexity of the
product, and completeness of the installation and configuration information.
The DIGITAL HiTest process thoroughly examined all aspects of the installation of this
HiTest Suite. The installation procedures that were used are documented in Chapter 4.
The following problems were found during installation:
•
With the maximum configuration, it is possible that the RAID controller may not identify
the disks. (Provided that the installation instructions documented in Chapter 4 are
followed, this problem will not occur.) In the event that this problem
does
occur, the
correct way to resolve this problem is documented in Chapter 6.