HSG80 ACS Solution Software Version 8.7 for Compaq Tru64 UNIX Installation and Configuration Guide

Planning Storage Configurations
2–32 HSG80 ACS Solution Software Version 8.7 for Compaq Tru64 UNIX Installation and
Configuration Guide
Table 2–7 shows a few examples of chunk size selection.
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Increasing Sequential Data Transfer Performance
RAID 0 and RAID 0+1 sets intended for high data transfer rates should use a
relatively low chunk size (for example: 67 sectors). RAID 5 sets intended for high data
rate performance should use a relatively large number (for example: 253 sectors).
Save Configuration
The SAVE CONFIGURATION switch is for a single-controller configuration only.
This switch reserves an area on each of the disks for the container being initialized.
The controller can write subsystem configuration data on this area. If the controller is
replaced, the new controller can read the subsystem configuration from the reserved
areas of disks.
If you specify SAVE_CONFIGURATION for a multi-device storageset, such as a
stripeset, the complete subsystem configuration is periodically written on each disk in
the storageset.
CAUTION: If user data already exists on a storageset, do NOT reinitialize it with the
save configuration option, as this will change the site and position of the user data on
the storageset. Always back up user data prior to reinitializing any storageset.
The SHOW DEVICES FULL command shows which disks are used to backup configuration
information.
IMPORTANT: DO NOT use SAVE_CONFIGURATION in dual redundant controller installations.
It is not supported and may result in unexpected controller behavior.
Table 2–7: Example Chunk Sizes
Transfer Size
(KB)
Small Area of I/O
Transfers
Unknown
Random Areas of I/O
Transfers
2 41 59 79
4 79 113 163
8 157 239 317