Interview Questions.

Question 1. How Can You Define A Cluster And What Are Its Basic Types?

Answer :

A cluster is two or extra computers (known as nodes or individuals) that work together to carry out a undertaking.

There are four major sorts of clusters:

Storage
High availability
Load balancing
High performance
Question 2. What Is Storage Cluster?

Answer :

Storage clusters provide a constant report gadget picture across servers in a cluster, permitting the servers to simultaneously read and write to a single shared report gadget. 
A garage cluster simplifies garage management by way of limiting the set up and patching of packages to one document gadget. 
The High Availability Add-On presents garage clustering along with Red Hat GFS2
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Question 3. What Is High Availability Cluster?

Answer :

High availability clusters provide fairly available services by means of doing away with unmarried factors of failure and by way of failing over offerings from one cluster node to every other in case a node becomes inoperative. 
Typically, services in a high availability cluster read and write facts (thru examine-write set up file structures). 
A excessive availability cluster should keep statistics integrity as one cluster node takes over control of a carrier from some other cluster node. 
Node disasters in a high availability cluster are not visible from clients outdoor the cluster. 
High availability clusters are once in a while called failover clusters.
Question 4. What Is Load Balancing Cluster?

Answer :

Load-balancing clusters dispatch community carrier requests to a couple of cluster nodes to balance the request load a number of the cluster nodes. 
Load balancing gives value-effective scalability because you may match the variety of nodes in step with load requirements. If a node in a load-balancing cluster becomes inoperative, the burden-balancing software program detects the failure and redirects requests to other cluster nodes. 
Node disasters in a load-balancing cluster aren't seen from clients out of doors the cluster. 
Load balancing is to be had with the Load Balancer Add-On.
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Question five. What Is A High Performance Cluster?

Answer :

High-performance clusters use cluster nodes to carry out concurrent calculations. 
A excessive-performance cluster lets in programs to work in parallel, consequently improving the overall performance of the applications. 
High performance clusters are also referred to as computational clusters or grid computing.
Data Center Management Interview Questions
Question 6. How Many Nodes Are Supported In Red Hat 6 Cluster?

Answer :

A cluster configured with qdiskd supports a maximum of 16 nodes. The motive for the limit is due to scalability; growing the node remember increases the amount of synchronous I/O contention on the shared quorum disk device.

Question 7. What Is The Minimum Size Of The Quorum Disk?

Answer :

The minimal size of the block tool is 10 Megabytes.

Unix/Linux Tutorial Red Hat Linux Essentials Interview Questions
Question 8. What Is The Order In Which You Will Start The Red Hat Cluster Services?

Answer :

In Red Hat 4 :

service ccsd start
carrier cman start
service fenced begin
service clvmd begin (If CLVM has been used to create clustered volumes)
provider gfs start
provider rgmanager begin
In RedHat five :

provider cman start
provider clvmd start
service gfs start
service rgmanager start
In Red Hat 6 :

provider cman begin
provider clvmd begin
provider gfs2 start
service rgmanager start
Question 9. What Is The Order To Stop The Red Hat Cluster Services?

Answer :

In Red Hat four :

carrier rgmanager forestall
carrier gfs stop
carrier clvmd stop
provider fenced prevent
provider cman stop
provider ccsd forestall
In Red Hat 5

carrier rgmanager prevent
service gfs forestall
carrier clvmd forestall
carrier cman stop
In Red Hat 6 :

carrier rgmanager forestall
service gfs2 forestall
service clvmd forestall
carrier cman forestall
Red Hat Linux System Administration Interview Questions
Question 10. What Are The Performance Enhancements In Gfs2 As Compared To Gfs?

Answer :

Better performance for heavy usage in a single listing
Faster synchronous I/O operations
Faster cached reads (no locking overhead)
Faster direct I/O with preallocated files (supplied I/O length within reason big, inclusive of 4M blocks)
Faster I/O operations in preferred
Faster Execution of the df command, because of faster statfs calls
Improved atime mode to lessen the wide variety of write I/O operations generated with the aid of atime whilst as compared with GFS
GFS2 helps the subsequent capabilities.
Prolonged report attributes (xattr)
the lsattr() and chattr() attribute settings thru wellknown ioctl() calls
nanosecond timestamps
GFS2 makes use of much less kernel reminiscence.
GFS2 requires no metadata technology numbers.
Allocating GFS2 metadata does not require reads. Copies of metadata blocks in multiple journals are controlled by way of revoking blocks from the journal before lock release.
GFS2 consists of a miles less complicated log supervisor that knows nothing about unlinked inodes or quota changes.
The gfs2_grow and gfs2_jadd commands use locking to save you multiple instances running at the identical time.
The ACL code has been simplified for calls like creat() and mkdir().
Unlinked inodes, quota adjustments, and statfs changes are recovered with out remounting the magazine.
Question 11. What Is The Maximum File System Support Size For Gfs2?

Answer :

GFS2 is primarily based on sixty four bit architecture, which could theoretically accommodate an eight EB report system. 
However, the modern supported most size of a GFS2 document device for sixty four-bit hardware is one hundred TB. 
The modern-day supported most size of a GFS2 record gadget for 32-bit hardware for Red Hat Enterprise Linux Release 5.Three and later is sixteen TB. 
NOTE: It is higher to have 10 1TB record systems than one 10TB record device.

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Question 12. What Is The Journaling Filesystem?

Answer :

A journaling filesystem is a filesystem that continues a unique record referred to as a magazine this is used to restore any inconsistencies that occur because the result of an flawed shutdown of a laptop.

In journaling report structures, each time GFS2 writes metadata, the metadata is dedicated to the magazine before it's miles put into place. 

This ensures that if the gadget crashes or loses energy, you will get better all the metadata when the journal is routinely replayed at mount time.

GFS2 calls for one magazine for every node inside the cluster that wishes to mount the record device. For instance, when you have a 16-node cluster but need to mount only the document system from two nodes, you need handiest  journals. If you want to mount from a 3rd node, you can usually upload a journal with the gfs2_jadd command.

System Administration Interview Questions
Question 13. What Is The Default Size Of Journals In Gfs?

Answer :

When you run mkfs.Gfs2 without the dimensions attribut for magazine to create a GFS2 partition, by way of default a 128MB size magazine is created which is enough for most of the packages

In case you plan on reducing the size of the journal, it is able to severely have an effect on the overall performance. Suppose you lessen the size of the journal to 32MB it does not take a great deal report machine hobby to fill an 32MB magazine, and whilst the journal is complete, performance slows because GFS2 has to watch for writes to the storage.

Question 14. What Is A Quorum Disk?

Answer :

Quorum Disk is a disk-primarily based quorum daemon, qdiskd, that provides supplemental heuristics to decide node health.

With heuristics you can determine factors that are vital to the operation of the node inside the occasion of a community partition

For a three node cluster a quorum kingdom is gift untill 2 of the three nodes are lively i.E. Extra than 1/2. But what if due to some motives the 2d node additionally stops communicating with the the third node? In that case beneath a ordinary structure the cluster could dissolve and prevent running. But for challenge critical environments and such scenarios we use quorum disk in which a further disk is configured which is set up on all of the nodes with qdiskd carrier strolling and a vote fee is assigned to it.

So think in above case I actually have assigned 1 vote to qdisk so even after 2 nodes stops speaking with 3rd node, the cluster might have 2 votes (1 qdisk + 1 from 3rd node) which continues to be more than half of vote remember for a 3 node cluster. Now each the inactive nodes would be fenced and your third node might be nonetheless up and going for walks being a part of the cluster.

Question 15. What Is Rgmanager In Red Hat Cluster And Its Use?

Answer :

This is a provider termed as Resource Group Manager

RGManager manages and presents failover competencies for collections of cluster sources referred to as offerings, resource corporations, or useful resource bushes

it lets in administrators to define, configure, and reveal cluster offerings. In the event of a node failure, rgmanager will relocate the clustered service to another node with minimum service disruption

Red Hat Satellite Interview Questions
Question sixteen. What Is Luci And Ricci In Red Hat Cluster?

Answer :

luci is the server aspect of the Conga administration software
Conga is an incorporated set of software additives that offers centralized configuration and management of Red Hat clusters and storage
luci is a server that runs on one laptop and communicates with multiple clusters and computer systems thru ricci
ricci is the consumer element of the Conga administration utility
ricci is an agent that runs on each laptop (both a cluster member or a standalone computer) managed by way of Conga
This carrier desires to be strolling on all the consumer nodes of the cluster.
Question 17. What Is Cman In Red Hat Cluster?

Answer :

This is an abbreviation used for Cluster Manager. 
CMAN is a disbursed cluster manager and runs in each cluster node. 
It is answerable for tracking, heartbeat, quorum, voting and conversation among cluster nodes.
CMAN continues tune of cluster quorum via monitoring the be counted of cluster nodes.
Server Load Balancing Interview Questions
Question 18. What Are The Different Port No. Used In Red Hat Cluster?

Answer :

IP Port no.
Protocol
Component
5404,5405
UDP
corosync/cman
11111
TCP
ricci
21064
TCP
dlm (Distributed Lock Manager)
16851
TCP
Modclustered
8084
TCP
luci
4196,4197
TCP
rgmanager
Data Center Management Interview Questions
Question 19. How Does Networkmanager Service Affects Red Hat Cluster?

Answer :

The use of NetworkManager isn't supported on cluster nodes. If you have got hooked up NetworkManager on your cluster nodes, you need to either get rid of it or disable it.

# carrier NetworkManager forestall

# chkconfig NetworkManager off

The cman provider will not begin if NetworkManager is both strolling or has been configured to run with the chkconfig command

Question 20. What Is The Command Used To Relocate A Service To Another Node?

Answer :

clusvcadm -r service_name -m node_name

Advanced Linux Interview Questions
Question 21. What Is Split-brain Condition In Red Hat Cluster?

Answer :

We say a cluster has quorum if a majority of nodes are alive, communicating, and agree on the lively cluster participants. For instance, in a thirteen-node cluster, quorum is simplest reached if seven or greater nodes are speaking. If the seventh node dies, the cluster loses quorum and may not feature.
A cluster need to preserve quorum to save you cut up-mind troubles.
If quorum turned into not enforced, quorum, a conversation blunders on that same 13-node cluster may additionally purpose a scenario in which six nodes are running on the shared storage, even as some other six nodes also are working on it, independently. Because of the conversation errors, the two partial-clusters would overwrite areas of the disk and corrupt the document system.
With quorum rules enforced, most effective one of the partial clusters can use the shared garage, as a result defensive records integrity.
Quorum would not save you split-brain conditions, but it does decide who is dominant and allowed to characteristic in the cluster.
Quorum may be decided with the aid of a aggregate of speaking messages via Ethernet and thru a quorum disk.
Question 22. What Are Tie-breakers In Red Hat Cluster?

Answer :

Tie-breakers are additional heuristics that allow a cluster partition to decide whether or now not it's miles quorate in the event of a good-split - prior to fencing. 

With this type of tie-breaker, nodes now not most effective display each other, but also an upstream router that is on the equal direction as cluster communications. If the 2 nodes lose contact with each other, the only that wins is the only that could still ping the upstream router.That is why, even if the usage of tie-breakers, it's miles crucial to make sure that fencing is configured correctly.

CMAN has no inner tie-breakers for various motives. However, tie-breakers may be carried out the usage of the API.

Question 23. What Is Fencing In Red Hat Cluster?

Answer :

Fencing is the disconnection of a node from the cluster's shared storage. 
Fencing cuts off I/O from shared storage, consequently ensuring statistics integrity. 
The cluster infrastructure performs fencing through the fence daemon, fenced.
When CMAN determines that a node has failed, it communicates to other cluster-infrastructure components that the node has failed. 
Fenced, when notified of the failure, fences the failed node. 
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Question 24. What Are The Various Types Of Fencing Supported By High Availability Add On?

Answer :

Power fencing : fencing approach that uses a energy controller to energy off an inoperable node.
Garage fencing : A fencing method that disables the Fibre Channel port that connects storage to an inoperable node.
Other fencing : Several other fencing techniques that disable I/O or power of an inoperable node, such as IBM Bladecenters, PAP, DRAC/MC, HP ILO, IPMI, IBM RSA II, and others.
Red Hat Linux Essentials Interview Questions
Question 25. What Are The Lock States In Red Hat Cluster?

Answer :

A lock nation indicates the modern-day status of a lock request.

A lock is always in considered one of three states:

Granted — The lock request succeeded and attained the requested mode.
Converting — A purchaser attempted to trade the lock mode and the brand new mode is incompatible with an current lock.
Blocked — The request for a brand new lock could not be granted because conflicting locks exist.
A lock's kingdom is determined by its requested mode and the modes of the opposite locks at the same resource.

Question 26. What Is Dlm Lock Model?

Answer :

DLM is a brief abbreviation for Distributed Lock Manager.
A lock manager is a site visitors cop who controls get right of entry to to resources inside the cluster, including get right of entry to to a GFS record gadget.
GFS2 uses locks from the lock supervisor to synchronize get admission to to report machine metadata (on shared storage)
CLVM makes use of locks from the lock manager to synchronize updates to LVM volumes and quantity businesses (also on shared garage)
In addition, rgmanager uses DLM to synchronize service states.
With out a lock supervisor, there would be no manipulate over access to your shared storage, and the nodes in the cluster could corrupt every other's facts.
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