Performing An Issu; Overview; Issu Methods - HP 10500 Series Configuration Manual

Performing an ISSU

Unless otherwise stated, the term "upgrade" refers to both software upgrade and downgrade in ISSU.

Overview

The In-Service Software Upgrade (ISSU) feature upgrades software with a minimum amount of downtime.
ISSU is implemented on the basis of the following design advantages:
Separation of service features from basic functions—Device software is segmented into boot,
•
system, and feature images. The images can be upgraded individually.
Independence between service features—Features run independently. One feature can be added
•
or upgraded without affecting the operation of the system or other features.
Support for hotfix—Patch images are available to fix system bugs without a system reboot.
•
• Hardware redundancy—On a dual-MPU device or a multichassis IRF fabric, one MPU or member
device can be upgraded while other MPUs or member devices are providing services.
For more information about images, see "Upgrading software."

ISSU methods

ISSU methods are automatically determined depending on the compatibility between software versions.
ISSU supports the following upgrade types:
• Compatible upgrade—The running software version is compatible with the new software version.
This upgrade type supports the ISSU methods in
Incompatible upgrade—The running software version is incompatible with the new software
•
version. The two versions cannot run concurrently.
This upgrade type supports only one upgrade method (also called incompatible upgrade). This
method requires a cold reboot to upgrade both control and data planes. Incompatible upgrade
disrupts service if hardware redundancy is not available.
For information about identifying the ISSU method, see
Table 13 ISSU methods for compatible upgrade
ISSU method
Incremental upgrade:
•
Service Upgrade
•
File Upgrade
Description
Upgrades only user mode processes that have differences between the new and old
software versions. Backup processes and a main/backup process switchover are
required for service continuity.
•
Service upgrade—Upgrades service features. The upgrade does not affect the
operation of the features that are not being upgraded.
•
File upgrade—Upgrades hidden system program files. The system can provide
services during the upgrade.
133
Table 13.
"Identifying the ISSU method."