25.11.1 System configurations unable to perform system switchover
(1) System configuration able to perform system switchover
Figure 25-51 shows a system configuration that can perform system switchover.
Figure 25-51 System configuration able to perform system switchover
![[Figure]](figure/zu280080.gif)
- Explanation
- The fiber optic cable of each server machine is connected to the two fiber optic cables that connect to the shared disk unit (CR80). Locks operate correctly with this system configuration.
(2) System configurations unable to perform system switchover
Figures 25-52 and 25-53 show system configurations that cannot perform system switchover.
Figure 25-52 System configuration unable to perform system switchover (1)
![[Figure]](figure/zu280090.gif)
- Explanation
- If an optical HUB is placed between CR80 and the server machines, even if server machine 1 is in reserved status, its reserved status is released when server machine 2 restarts. This occurs because server machine 2 generates a LIP that affects server machine 1.
Figure 25-53 System configuration unable to perform system switchover (2)
![[Figure]](figure/zu280100.gif)
- Explanation
- Because a HUB is being used, the LIP that is generated when the system restarts releases the lock and does not operate properly.
- In the case of SWITCH, LIP is performed independently on each server so it operates properly.
- When using a Fiber-HUB, LIP causes an error in the lock.
- Note
- LIP is valid on all devices that are connected to the loop. Therefore, the lock may not be performed properly when two CR80 units are connected or multiple server machines and one CR80 unit are connected via a HUB.