HP P6000 Cluster Extension Software Administrator Guide (5697-0986, June 2011)

0001-6e12-0000-7000-031a-0000"
---- Sample UCF.cfg end
Timing considerations
P6000 Cluster Extension Software gives priority to storage system operations over cluster software
operations. If P6000 Cluster Extension is invoked during a DR group member resynchronization
operation (merging) or is gathering information about the remote storage system, it waits until the
requested status information is reported. This ensures the priority of data integrity over cluster software
failover behavior.
Because the failover timing depends on the configuration of your HP P6000/EVA SMI-S server and
P6000 Command View environment and the settings in the UCF.cfg file, you must evaluate the
following considerations:
• P6000 Cluster Extension uses HP SMI-S to communicate with the HP P6000/EVA storage system,
depending on the settings of the SMI-S request timeout property, and the number of managed
P6000/EVA arrays, the online operation could time out. This can also happen if clxevarun is
used in a script or called by another program and the HP SMI-S server instance(s) cannot be
reached.
• In the UCF.cfg file, if the ApplicationStartup attribute is set to RESYNCWAIT, P6000 Cluster
Extension tries to resynchronize disk pairs and waits until the DR group is in a normal state. De-
pending on the amount of data to be transferred, it could take hours to resynchronize. If this is the
case, clxevarun may take some time to return. Do not stop clxevarun; use the SSSU command
show DR_GROUP full-path/dr-group-name or the P6000 Command View or P6000
Continuous Access GUI to check the status of the DR groups.
• Depending on the amount of data that is out of sync between the source and destination vdisk
while the P6000 Continuous Access replication link(s) is unavailable, a merge/resynchronization
or a full copy operation is initiated when the P6000 CA replication link(s) is re-established. The
amount of delta data to be transferred between the source and destination vdisk could be large
enough for the copy process to take some time.
• To prevent the failover timeout trigger from terminating a failover command before it is finished,
the time to copy an average amount of daily processed (write) data should be measured and the
resource online timeout interval should be adjusted accordingly. Use only one (the slowest) link
used for P6000 Continuous Access to measure the copy time. This ensures that the average daily
generated data can be transferred fast enough from the remote P6000/EVA storage system, even
in the event of a single surviving replication link between the P6000/EVA storage systems.
In general, because the failover environment is dispersed into two (or more) data centers, the failover
time cannot be expected to be the same as it would be in a single data center with a single shared
disk device.
Restrictions for customized implementations
The following restrictions apply when using the P6000 Cluster Extension CLI:
• The P6000 Cluster Extension CLI command clxevarun must be invoked before the associated
disk resources are activated.
• Associated disk resources must not be activated on any other system. If other disk resources are
activated, P6000 Cluster Extension may remove write-access rights for those disk devices (putting
them in read-only mode).
CLI commands and utilities90