VMware vsphere 5.1 cluster Walkthrough (ii) high-availability components

Now that we know the prerequisites for HA and how to configure ha, then we'll describe what components ha consists of, so keep in mind that these are still areas of high concern, and there are more to wait to see in the following sections, the figure below describes the clusters of two ESXi hosts and the key components of HA.

The constituent components of Figure 4:ha

As you can see, the ha of Vsphere 5.0 is composed of three major components

Fdm

Hostd

Vcenter

Fdm

First is the most important component in the HA architecture, FDM (Fault Domain Manager), which is the agent for Ha, replacing the agent AAM (Legato's automated availability Manager) prior to vSphere5.0 ha.

The FDM agent is responsible for many tasks, such as the transfer of resource information between hosts and the state of the virtual machine. The host of the appropriate HA for the communication cluster, FDM also handles the heartbeat mechanism, the placement of virtual machines, the restart of virtual machines, logins, and more, and so on, we will not discuss this alone too deeply, because we think it will make it a lot more complicated.

When the HA feature is enabled, it seems to us that FDM is a very important agent on the ESXi host, and that Ha adds extra flexibility and engineers will recognize its importance. Contrary to AAM, FDM uses a single threaded agent, however, FDM produces a watchdog program, if the agent fails, the watchdog program will not be noticed by anyone, restart the agent to ensure that the HA function, the agent in the path of failure will have a momentary network interruption, in terms of flexibility, After the network failure, the intranet host will automatically communicate with other hosts in another way (in the case of Management network redundancy)

Like Vsphere 5.0, HA does not rely on DNS and IP addresses, which is a major improvement for FDM, meaning that the HA limit ESXi host naming rules are lifted (ESXi host FQDN is limited to 26 characters before Vsphere 5.0), This does not mean that the vcenter ESXi hosts need to register their IP addresses, and best practices recommend registering the FQDN of the ESXi host in Vcenter, although HA is not dependent on DNS, many other services are still dependent and, most importantly, A host is properly registered in vcenter and a valid FQDN makes it easier to monitor and troubleshoot errors.

Basic design Principles

Although HA is not dependent on DNS, it is still recommended to register the FQDN of the host

Another major change in FDM is the creation of logs, some of you may never realize this, some of you may find it difficult, vsphere 5.0, ha log log will not be sent to Syslog, Vsphere 5.0 brings the principle of log generation, A separate log log will be created and placed in a directory with all other operations logs, called Fdm.log, which is stored under the/var/log path, as shown in Figure five

Figure 5:ha Log file