The authkeys file must be owned by root and be chmod The actual format of the authkeys file is very simple; it's only two lines. There is an auth directive with an associated method ID number, and there is a line that has the authentication method and the key that go with the ID number of the auth directive. There are three supported authentication methods: crc, md5 and sha1.
Listing 1 shows an example. You can have more than one authentication method ID, but this is useful only when you are changing authentication methods or keys. Make the key long—it will improve security and you don't have to type in the key ever again. The next file to configure is the ha. The contents of this file should be the same on all nodes with a couple of exceptions.
Heartbeat ships with a detailed example file in the documentation directory that is well worth a look. Also, when creating your ha. Don't move them around! Two different example ha. The first thing you need to specify is the keepalive—the time between heartbeats in seconds.
I generally like to have this set to one or two, but servers under heavy loads might not be able to send heartbeats in a timely manner. So, if you're seeing a lot of warnings about late heartbeats, try increasing the keepalive. The deadtime is next. This is the time to wait without hearing from a cluster member before the surviving members of the array declare the problem host as being dead. Next comes the warntime. Sometimes, when all members of a cluster are booted at the same time, there is a significant length of time between when Heartbeat is started and before the network or serial interfaces are ready to send and receive heartbeats.
The optional initdead directive takes care of this issue by setting an initial deadtime that applies only when Heartbeat is first started. You can send heartbeats over serial or Ethernet links—either works fine. I like serial for two server clusters that are physically close together, but Ethernet works just as well. The configuration for serial ports is easy; simply specify the baud rate and then the serial device you are using. The serial device is one place where the ha. If you don't know the tty to which your serial port is assigned, run the following command:.
If you have several serial ports, experiment to find out which is the correct one. If you decide to use Ethernet, you have several choices of how to configure things.
For simple two-server clusters, ucast uni-cast or bcast broadcast work well. If I am using a crossover cable to connect two hosts together, I just broadcast the heartbeat out of the appropriate interface.
Here is an example bcast line:. There is also a more complicated method called mcast. This method uses multicast to send out heartbeat messages. Check the Heartbeat documentation for full details. If set to off, when the primary node comes back, it will be the secondary. It's a toss-up as to which one to use.
My thinking is that so long as the servers are identical, if my primary node fails, then the secondary node becomes the primary, and when the prior primary comes back, it becomes the secondary. Moving on, when Heartbeat thinks a node is dead, that is just a best guess. Sometimes, there's only one way to be sure whether a node is dead, and that is to kill it. In computer clusters , a heartbeat network is a private network which is shared only by the nodes in the cluster , and is not accessible from outside the cluster.
It is used by cluster nodes in order to monitor each node's status and communicate with each other messages necessary for maintaining operation of the cluster. Additionally, what is quorum in cluster Linux? The cluster configuration database, also called the quorum , tells the cluster which physical server s should be active at any given time. A Linux cluster is a connected array of Linux computers or nodes that work together and can be viewed and managed as a single system.
A server cluster is a group of linked servers that work together to improve system performance, load balancing and service availability. Create cluster on active node. Add a node to cluster. Add fencing to cluster. Configure failover domain. Add resources to cluster. Sync cluster configuration across nodes.
Start the cluster. Heartbeat as a Cluster Messaging Layer. Heartbeat is a daemon that provides cluster infrastructure communication and membership services to its clients. This allows clients to know about the presence or disappearance! How many types of quorums are there in a cluster? There are four quorum types.
What is floating IP in Linux? Part of a highly available infrastructure is being able to immediately point an IP address to a redundant server. This is now possible with the addition of Floating IPs. What is heartbeat IP? A heartbeat is a type of a communication packet that is sent between nodes. Being able to support multiple nodes in a cluster is crucial, as is monitoring.
Resource monitoring ensures that the failure of a service provided by a node can be detected even without the node actually "dying. Dependencies, otherwise called " constraints " are important, as you might never want database servers to run on the same node as Web servers, or you might want to always have data replication services run only on nodes that are running the database services.
The version of Heartbeat available today is a stable and effective way of ensuring that two nodes in a cluster act in a coordinated manner.
Each server runs the Heartbeat daemon and exchange messages called Heartbeats that inform the other machine that the sender is alive. In the event of the primary node failing, the back-up node Heartbeat is responsible for transferring any IP addresses that must be available after failover. A highly reliable communications channel is required to avoid the split-brain, or less sexily the partitioned, cluster problem.
In a split-brain situation both servers are alive and functioning, but both also believe the other is dead because the Heartbeats can no longer be seen. You now have the problem of both servers trying to provide the same services and use the same IP address for crucial client services. Even worse is when both servers share disk resources and compete for access to the same data at the same time.
Stonith uses a controllable power control device such as the Western Telematic network power switch we discussed ages ago.
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