504 Appendix B
Administration of MC/ServiceGuard
How MC/ServiceGuard Works
Figure B-1 MC/ServiceGuard Package Switchover: Before the Switch
Assume that node 1 fails. Node 2 is an adoptive node for Package A, but
for Package B no adoptive node is specified; therefore the applications
specified in Package B will not be transferred in the event of node failure.
However, Package B will be protected from a possible network failure by
local network switching.
NOTE Transfering control of a package to another node does not transfer the
program counter. Processes in a transferred package will restart from
the beginning. If necessary, all processes in a package must be written so
that they can detect such a restart.
When a node fails, the CPU is halted immediately using a Transfer Of
Control (TOC) which is an immediate halt without a graceful shutdown.
Bridge
Package A
Package D
Package C
Root 1
Root 2
Root 3
Root 2
Mirror
Node 1
Node 2
Node 3
Package
A Disk
Package
F Disk
Package
E Disk
Package
D Disk
Package
C Disk
Package
B Disk
Package
A Mirror
Package
D Mirror
Package
F Mirror
Package
E Mirror
Package
B Mirror
Package
C Mirror
LAN 0
LAN 1
Package B
Package E
Package F
