6.5

Table Of Contents
MaxDiskUsage Errors
vCenter Server Heartbeat uses queues to buer the ow of replication data from the active server to the passive
server. This conguration provides resilience in the event of user activity spikes, VMware Channel bandwidth
restrictions, or VMware Channel drops across a WAN deployment. Some types of le write activity also require
buering as they can cause a sharp increase in the amount of channel trac. The queues are called the send
queue (on the active server) or the receive queue (on the passive server).
Send Queue
vCenter Server Heartbeat considers the active servers send queue as unsafe because the data in this queue
has not yet been replicated across the VMware Channel to the passive server and therefore could be lost in the
event of a failover. As a result of failover, some data loss is inevitable, with the exact amount depending on
the relationship between available VMware Channel bandwidth and the required data transmission rate. If
the required data transmission rate exceeds available VMware Channel bandwidth, the send queue lls. If the
available VMware Channel bandwidth exceeds the required data transmission rate, the send queue empties.
This situation is most commonly seen in a WAN environment, where VMware Channel bandwidth is restricted.
In a LAN that normally has high bandwidth on a dedicated channel, the size of the send queue is zero or near
zero most of the time. On a server not protected with vCenter Server Heartbeat, all data is technically unsafe
and subject to loss if the server fails.
Receive Queue
The passive servers receive queue is considered safe because the data in this queue already was transmitted
across the VMware Channel from the active server, and is not lost in the event of a failover, which applies all
updates to the passive server as part of the process.
Both send and receive queues are stored on disk by default in the <VMware vCenter Server Heartbeat Install
Directory>\R2\log directory, with a quota congured for the maximum permitted queue size (by default, 1GB
on each server). You can congure both the queue location and the quota.
Two methods to set the queue size:
Using vCenter Server Heartbeat Console
1 Start vCenter Server Heartbeat
2 Open the vCenter Server Heartbeat Console, and select Data: Trac Queues.
3 Click Congure.
4 Congure the Allow a maximum value and click OK.
5 Shut down and restart vCenter Server Heartbeat to eect the change. You are not required to stop protected
applications.
Using the Server Conguration wizard
1 Shut down vCenter Server Heartbeat.
2 Open the Server Conguration wizard and select the Logs tab.
94 VMware, Inc.
Administrator Guide