Avago Technologies Syncro 9361-8i - Manual (Page 58)

Avago Technologies
- 58 -
Syncro CS 9361-8i and Syncro CS 9380-8e Solution User Guide 
October 2014
Chapter 3: System Administration
Understanding Failover Operations
The following figure shows the condition of the two server nodes after the failover.
Figure 40 After Failover from Server A to Server B
After failover, the cluster status is as follows, in terms of managing the drive group and the VDs:
 All shared VDs in A-DG0 have failed over and are now managed by Server B.
 VD3 in B-DG0 is still managed by Server B.
After failover, the operating system perspective is as follows:
 The operating system on Server B manages all shared VDs and any exclusive Server B VDs.
After failover, the operating system perspective of I/O transactions is as follows:
 Failover Cluster Manager has moved the I/O transactions for VD2 on A-DG0 to Server B.
 Server B continues to run I/O transactions on B-DG0:VD3.
 I/O transactions that rely on the exclusive A-DG0:VD1 on Server A fail because exclusive volumes do not move
with a failover
NOTE When Server A returns, the management and I/O paths of the
pre-failover configurations are automatically restored.
The following sections provide more detailed information about planned failover and unplanned failover.
3.2.1 Understanding and Using Planned Failover
A planned failover occurs when you deliberately transfer control of the drive groups from one controller node to the
other. The usual reason for initiating a planned failover is to perform some kind of maintenance or upgrade on one of
the controller nodes—for example, upgrading the controller firmware, as described in the following section. A
planned failover can occur when there is active data access to the shared drive groups.
Before you start a planned failover on a Syncro CS system, be sure that no processes are scheduled to run during that
time. Be aware that system performance might be impacted during the planned failover.