VERITAS Volume Manager 3.5 Administrator's Guide (September 2004)

Administering Cluster Functionality

Cluster Initialization and Conﬁguration

Chapter 10 353

Node Shutdown

Although it is possible to shut down the cluster on a node by invoking the

shutdown procedure of the node’s cluster monitor, this procedure is

intended for terminating cluster components after stopping any

applications on the node that have access to shared storage. VxVM

supports clean node shutdown, which allows a node to leave the

cluster gracefully when all access to shared volumes has ceased. The host

is still operational, but cluster applications cannot be run on it.

The cluster functionality of VxVM maintains global state information for

each volume. This enables VxVM to determine which volumes need to be

recovered when a node crashes. When a node leaves the cluster due to a

crash or by some other means that is not clean, VxVM determines which

volumes may have writes that have not completed and the master node

resynchronizes these volumes. It can use dirty region logging (DRL) or

FastResync if these are active for any of the volumes.

Clean node shutdown must be used after, or in conjunction with, a

procedure to halt all cluster applications. Depending on the

characteristics of the clustered application and its shutdown procedure, a

successful shutdown can require a lot of time (minutes to hours). For

instance, many applications have the concept of draining, where they

accept no new work, but complete any work in progress before exiting.

This process can take a long time if, for example, a long-running

transaction is active.

When the VxVM shutdown procedure is invoked, it checks all volumes in

all shared disk groups on the node that is being shut down. The

procedure then either continues with the shutdown, or fails for one of the

following reasons:

• If all volumes in shared disk groups are closed, VxVM makes them

unavailable to applications. Because all nodes are informed that

these volumes are closed on the leaving node, no resynchronization is

performed.

• If any volume in a shared disk group is open, the shutdown operation

in the kernel waits until the volume is closed. There is no timeout

checking in this operation.