Knowledge Base

The bottle neck lies between the VMware Channel NIC and the disk subsystem on the passive server. Replication traffic therefore passes across the channel faster than it can be written to disk on the passive server. It is buffered temporarily in the passive server (safe) queue. As before, if this situation persists, the size of the queue may eventually exceed the disk quota allotted for it.

If the passive server is much less powerful than the active server, in terms of processor speed, RAM or disk performance, it may lag behind the active server during periods of high replication activity. If you suspect this is the case, it may be useful to monitor one or more Windows performance counters to determine that component is experiencing sustained high activity. Intensive page file use or persistently large disk queue length may indicate a problem, which can be solved by upgrading one or more physical components of the server.

Note: Either server can be active or passive. If the Secondary server is more powerful than the Primary server, hardware-related issues might only occur while the Secondary server is in the active role.

Note: The selected path is applied to all VMware vCenter Server Heartbeat queues on both servers.

This may alleviate the symptoms of this problem by simply increasing the amount of disk space allotted to the queues. However, if you have reason to suspect that a hardware issue is the root of the problem, it is better to correct that problem at the source if possible.

It is also possible for the size of the passive server queue to increase sharply in response to certain types of file write activity on the active server. This is most obvious when VMware vCenter Server Heartbeat is replicating a large number of very small updates (typically a few bytes each) - the volume of update traffic may be far greater than the physical size of the files on the disk, and so the passive server queue in particular may become disproportionately large. This pattern of disk activity is often seen during the population of Full-Text Catalogs in Microsoft SQL Server.

Increase the amount of disk space available for the queues, moving the queues to their own physical disk or upgrading memory or the disk subsystem may also help to alleviate the issue.

VMware vCenter Server Heartbeat requires a certain amount of system resource for its own basic operations and requires some additional resources for processing replication traffic. This is in addition to the resources used by Windows and other applications running on the server (including critical applications protected by VMware vCenter Server Heartbeat). It is always a good idea to ensure that there are sufficient resources for all of the applications and services running on such a server, to provide maximum performance, stability, and resilience in the face of changing client, server, and network activity.