Understanding takeover

Takeover process

The takeover process is shown in the following table.

Stage Description
1 One of these three things happen:
  • One filer in a cluster undergoes a hardware or power failure and can't reboot. That filer is the failed filer, and the surviving filer is the takeover filer.
  • An operator issues the cf takeover command from a filer. The filer from which the command was issued becomes the takeover filer; the other filer becomes the failed filer.
  • An operator issues the halt command without the -f option.
2 The takeover filer reserves the disk drives on its FC-AL B loop (which is the failed filer's FC-AL A loop) so that they do not receive commands from the failed filer.
3 The takeover filer creates a virtual filer that takes over the resources and identity of the failed filer and executes the equivalent of a reboot of the virtual filer. For example, it uses network interface information from the failed filer's configuration files to duplicate the failed filer's network services.
4 The virtual filer goes through a process similar to the reboot process.
  • All filer information preserved across filer reboot is preserved in a takeover.
  • Filer information that is lost in a reboot, such as CIFS connection state, is lost in a takeover.
5

Users of the failed filer experience the effects of a reboot of the failed filer, and then client service continues.

Messages indicating a successful takeover

During a typical takeover, the cluster monitor issues messages like the following on the console of the takeover filer. In this case, the partner of filer1 was halted.

filer1> Tue Jul 21 23:02:02 GMT [filer1: cf_main]: Cluster monitor: 
partner halted

Tue Jul 21 23:02:11 GMT [filer1: cf_main]: Cluster monitor: partner 
not responding

Timeout messages such as the following appear as filer1 waits for signs of life from its partner:

Tue Jul 21 23:02:34 GMT GMT [filer1: cf_main]: Cluster monitor: 
takeover scheduled in 30 seconds

Then the following messages appear:

Tue Jul 21 23:03:06 GMT [filer1: cf_takeover]: Cluster monitor: 
takeover started

Reboot messages follow as the virtual filer boots up, then the following message appears and indicates a successful takeover:

Tue Jul 21 23:03:22 GMT [filer1: cf_takeover]: Cluster monitor: 
takeover completed

filer1(takeover)>

Takeover result diagram

The following figure shows the state of a cluster after a takeover of Filer 1 by Filer 2. 








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Part No. 210-02334
File: clust5.htm
Last updated: 02/24/99 12:16:47