DiskGroupSnap agent notes
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DiskGroupSnap agent notes

Configuration considerations

Keep the following recommendations in mind:

• Do not bring the DiskGroupSnap resource online in the SystemZone where the application service group is online.
• When you create the fire drill service group, in general use the same attribute values that you use in the application service group.

  However, the BlockDevice attribute of the Mount resource and the DiskGroup attribute of the DiskGroup resource change between the application's service group and the fire drill's service group. You must append an _fd to the original disk group name for the disk group name that the fire drill uses. For example, if dg01 is the disk group's name in the application service group, the attributes in the fire drill resemble those in Sample resource values for a DiskGroupSnap resource.

  Sample resource values for a DiskGroupSnap resource shows the changes to resource values for the fire drill service group, note that the Volume resource is not included.

      Sample resource values for a DiskGroupSnap resource

Agent limitations

The following limitations apply to the DiskGroupSnap agent:

• The online and offline operations of the DiskGroupSnap resource invokes VCS action entry points to run VxVM commands to detach/reattach the fire drill site. Since VxVM requires that these commands are run on the node where the disk group is imported, the disk group has to be imported on some node in the cluster before these operations.
• If you attempt to shut down the node where you brought the fire drill service group online, the node goes to a leaving state and the VCS engine attempts to take all the service groups offline on that node. At this point, the VCS engine rejects all action entry point requests. Therefore, during offline the DiskGroupSnap agent cannot invoke the action to reattach the fire drill site to the target diskgroup. The agent logs a message that the node is in a leaving state and then removes the lock file. The agent's monitor function declares that the resource is offline. After the node restarts, the fire drill site still remains detached from the diskgroup and you must manually reattach it.
• If you halt the node while the DiskGroupSnap resource's service group is still online, the VxVM site used for the fire drill remains detached after the node is brought up. You must manually reattach the fire drill site to the original diskgroup at the primary site.
• Before you shut down or stop VCS locally on the node where the fire drill service group is online, you must take the fire drill service group offline. Otherwise, after the node restarts you must manually reattach the fire drill site to the disk group that is imported at the primary site.