Top 100+ Pacemaker Interview Questions And Answers
Question 1. What Is Pacemaker?
Pacemaker is a cluster useful resource supervisor. It achieves most availability on your cluster services (sources) with the aid of detecting and convalescing from node and resource-level disasters by utilising the messaging and club abilities furnished by means of your chosen cluster infrastructure (both Corosync or Heartbeat).
Question 2. What Are Key Features Of Pacemaker ?
Pacemaker's key features consist of:
Detection and recovery of node and service-stage screw ups
Storage agnostic, no requirement for shared storage
Resource agnostic, some thing that may be scripted can be clustered
Supports STONITH for making sure data integrity
Supports huge and small clusters
Supports both quorate and useful resource driven clusters TODO: quorum-pushed?
Supports nearly any redundancy configuration
Automatically replicated configuration that can be updated from any node
Ability to specify cluster-wide provider ordering, colocation and anti-colocation
Support for advanced offerings kind
Clones: for services which need to be active on more than one nodes
Multi-nation: for services with a couple of modes (eg. Grasp/slave, number one/secondary)
Unified, scriptable, cluster shel
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Question three. What Are The Types Of Pacemaker Clusters ?
Pacemaker helps almost any redundancy configuration along with Active/Active, Active/Passive, N+1, N+M, N-to-1 and N-to-N.
Question four. What Are The Basic Components Of Pacemaker ?
Pacemaker consists of four key additives :
CIB ( Cluster Information Base)
CRMd ( Cluster Resource Management daemon)
PEngine ( PE or Policy Engine)
The CIB uses XML to represent both the cluster's configuration and modern kingdom of all assets within the cluster. The contents of the CIB are automatically stored in sync throughout the entire cluster and are utilized by the PEngine to compute the appropriate kingdom of the cluster and how it have to be accomplished.Pacemaker centralizes all cluster choice making through electing one of the CRMd times to act as a grasp. Should the elected CRMd process (or the node it's miles on) fail… a new one is quickly set up.
STONITH is an acronym for Shoot-The-Other-Node-In-The-Head and is commonly implemented with a faraway electricity switch. In Pacemaker, STONITH gadgets are modeled as sources (and configured within the CIB) to allow them to be without problems monitored for failure.
Question 5. How To Check The Current State Of The Cluster In Pacemaker ?
crm_mon utility is used to display the contemporary kingdom of an energetic cluster. It can show the cluster popularity by using node or with the aid of aid and can be used in either single-shot or dynamically-updating mode. There are also modes for displaying a list of the operations achieved (grouped by using node and useful resource) in addition to data approximately failures.
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Question 6. How To Add And Modify The Cluster Resource Configuration In Pacemaker ?
Using crm application we can alternate the cluster assets as display within the under example:
crm configure belongings stonith-enabled=false; (disabled stonith i.E fencing useful resource)
Question 7. How To Check The Configuration Of The Pacemaker Cluster ?
crm configure display
crm configure show xml
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Question eight. How To Add Virtual Ipadress/floating Ip Resource In The Pacemaker Cluster ?
crm configure primitive ClusterIP ocf:heartbeat:IPaddr2 params ip=192.168.122.120 cidr_netmask=32 op monitor c language=30s 192.168.122.120 is the floating address, we've given the imaginative name ClusterIP and tell the cluster to test that its running every 30 seconds.The different crucial piece of records here is ocf:heartbeat:IPaddr2, This tells Pacemaker three things approximately the useful resource you need to feature. The first field, ocf, is the standard to which the aid script conforms to and in which to discover it. The 2d subject is specific to OCF resources and tells the cluster which namespace to locate the resource script in, in this situation heartbeat. The final subject indicates the name of the useful resource script.
Question nine. Which Command Is Used To Check The Validity Of The Cluster Configuration ?
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Question 10. How To Find All The Ocf Resource Agents Provided By Pacemaker And Heartbeat ?
crm ra listing ocf pacemaker & crm ra list ocf heartbeat.
Question eleven. What Is Stonith ?
STONITH is an acronym for Shoot-The-Other-Node-In-The-Head and it protects your records from being corrupted via rogue nodes or concurrent get admission to. Just due to the fact a node is unresponsive, this doesn’t suggest it isn’t accessing your information. The only manner to be 100% sure that your statistics is safe, is to use STONITH so we can be sure that the node is sincerely offline, before allowing the facts to be accessed from some other node.
STONITH also has a function to play within the event that a clustered service cannot be stopped. In this case, the cluster makes use of STONITH to pressure the whole node offline, thereby making it secure to start the service else in which.
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Question 12. What Is Corosync ?
The Corosync Cluster Engine is an open source assignment Licensed beneath the New BSD License derived from the OpenAIS task.CoroSync carries the infrastructure (which include interprocess communique and community protocols) that was once a part of OpenAIS.
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Question thirteen. What Is The Purpose Of Pacemaker High-availability Clustering?
As the name of the challenge indicates, the purpose of Pacemaker high-availability clustering is to make sure that essential assets receive expanded availability. Without a clustering answer, a service may additionally fail at the moment the server crashes. If the carrier is configured as a useful resource in Pacemaker clustering, Pacemaker ensures that the provider will still be to be had, even if a server to your network fails.
Question 14. What Hardware And Software Do I Need To Run Pacemaker?
You want at the least two servers that run Linux. Currently, Pacemaker is capable of guide as much as sixteen servers, but some humans run it on clusters that have masses of servers, which can be called nodes within the cluster. Virtually all Linux distributions are supported. But in case you need Enterprise support, Novell's SUSE Linux Enterprise Server is presently the only Linux distribution that has that capacity. The servers have to be set up in the identical LAN and, in most instances, a storage region network (SAN) is needed as well. For gold standard performance, you need a unique device this is capable of shutting down a server if wanted -- the STONITH device.
Question 15. Do I Need A San If I Want To Create A Cluster?
Clustering is about accelerated availability of offerings. To attain this purpose, a carrier have to be able to run on all servers in a cluster. The server need to additionally be able to access its configuration documents and records whilst it moves over to some other server. To make this clean, I exceedingly propose the usage of a SAN. Just placed the statistics and configuration files at the SAN and make certain all servers can reach the SAN. If you can not set up a SAN, there may be any other answer that offers shared get admission to to the documents. This may be a Network File System-primarily based answer or a synchronization solution, inclusive of rsync. If your records isn't too dynamic, you can even agenda a cron job to preserve the records and configuration in sync.
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Question 16. Why Do I Need Stonith?
Imagine that a conversation link fails in a -node cluster. Both servers may think the alternative one is down and begin servicing the resource which you need to be relatively available. If this aid wishes get admission to to the shared document device on the SAN, you could turn out to be with a state of affairs where each servers try and write to the equal record machine on the equal time. If you are the usage of a file gadget like Ext3, XFS or Ext4, this can purpose extreme file machine corruption. The STONITH tool makes positive that one of the servers is honestly close down earlier than a server can take over a resource from another. It does that by means of cutting the power to the server so it really is down. This feels like a peculiar answer, but it is lots better than having file gadget corruption.
Question 17. Is It Possible To Grant Different Servers Simultaneous Access To The Same Data?
You can try this if you are the usage of a unique cause cluster document system. Currently, there are of them: the Oracle Cluster File System (OCFS) 2 and the Global File System. Both are open source, so you can pick whichever system you choose. If, however, you're developing your cluster on Red Hat Linux, you will most probable work with GFS, which Red Hat advanced. If you use Novell's SUSE, you will be operating with OCFS2, because it is the handiest cluster-conscious document machine supported on SUSE. The unique factor approximately these report systems is that they have a shared cache. That manner if one server writes to the document gadget, the opposite server is aware of about it.
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