3.3.2 Preventing concurrent resets between multiple hosts
This subsection explains how to prevent concurrent host resets from occurring in a multi-standby configuration or a cluster hot-standby configuration.
In a configuration in which the multi-standby function is used to provide multiple standby servers for a single active server, concurrent resets on multiple hosts must be avoided.
You can also suppress resets if doing so reduces the number of hosts to below a certain minimum. For details about suppressing resets, see 3.3.4 Suppressing host resets.
- Organization of this subsection
(1) Configuration in which concurrent host resets might occur on multiple hosts
In a configuration consisting of three or more hosts, if the hosts are divided due to a failure in a monitoring path network component, a host failure might be detected in each of the network segments and all the hosts might be reset.
To avoid this possibility, you must define a unique reset issuance order for all hosts that belong to the hot-standby configuration. This reset issuance order is called the reset priority. You specify the reset priority in the HA Monitor environment settings.
Concurrent host resets might occur among multiple hosts in the following configurations:
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Configuration in which all hosts attempt reset
If all hosts detect a host failure at the same time due to a failure on the monitoring path, all hosts might issue a reset request at the same time and all the hosts might be reset.
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Configuration in which the multi-standby function is used
In a configuration that uses the multi-standby function to provide multiple standby servers for a single active server, all the standby servers running on multiple hosts detect a failure in the active system. This might result in concurrent host resets.
The following figure shows a configuration in which all hosts attempt reset.
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![[Figure]](GRAPHICS/F0000058.GIF)
In this configuration, if a failure occurs on all monitoring paths, all hosts are reset. If you specify a reset priority beforehand, HA Monitor determines the hosts to be reset and the order based on the reset priority.
(2) Required environment settings
You must specify host in the reset_type operand in the HA Monitor environment settings. If the multi-standby function is used, HA Monitor prevents concurrent resets based on the reset priority regardless of whether this operand is specified.
For details about the reset priority, see 4.2.3 Host reset when there are multiple standby systems.