3. Cluster
•In the most basic form, a cluster is two or more servers(physical or
virtual) that are configured as logical object and a single entity that
manage share resources and present them to the end user.
•Server that are member of a cluster is known as node
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4. Purpose of clustering
• The purpose of the clustering are to allows group of nodes to provide:
• Highly available, share capacity
• Highly performance
• Fault-tolerance
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5. Benefits of clustering
• The ability to survive a node crashing or going offline
• The ability to restart a VM or survive a VM crash
• Zero down time for any patching or maintenance to cluster nodes
• The ability to move and disperse the load of servers
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6. Cluster consists of
• Nodes(computers)
• Network
• OS
• Cluster middleware: Middleware such as MPI which permits compute
clustering programs to be portable to a wide variety of clusters
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7. Major types of clusters
•There are four major types of clusters:
•1.Storage
•2.High availability
•3.Load balancing
•4.High performance
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8. Storage clusters
• Storage clusters provide a consistent file system image across servers in a
cluster, allowing the servers to simultaneously read and write to a single
shared file system. A storage cluster simplifies storage administration by
limiting the installation and patching of applications to one file system.
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10. High-availability clusters
• •High-availability clusters provide continuous availability of services by
eliminating single points of failure and by failing over services from one cluster
node to another in case a node becomes inoperative.
• •Therefore, a high-availability cluster must maintain data integrity as one
cluster node takes over control of a service from another cluster node.
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11. Load-balancing clusters
• •Load-balancing clusters dispatch network service requests to
multiple cluster nodes to balance the request load among the
cluster nodes.
•• If a node in a load-balancing cluster becomes inoperative, the
load-balancing software detects the failure and redirects requests
to other cluster nodes.
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12. High-performance clusters
• High-performance clusters use cluster nodes to perform concurrent
calculations.
• A high-performance cluster allows applications to work in parallel, therefore
enhancing the performance of the applications.
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13. Clustering functionality
•Clustering is mix of software and hardware, and it can be hosted on
physical and virtual machines
•Windows server 2012 has the tools and components for deploying
the cluster
•Hyper-v cluster can supporting up to 64 nodes and 8000 VMs per
cluster
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14. Cluster share volumes
•Cluster share volumes(CSV) is a components of failover clustering
and was first introduced in server 2008 R2
•Their basic use is to simplify storage for virtual machine
•If we don’t have CSV in Hyper-v servers, than the storage will be
accessed only by the one node in the time
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15. Cluster share volumes
•The design of the CSV simplifies storage, so that any VMs can
access the same storage
•In widows server 2012 CSV allow multiple
•nodes to have read/write access to the volume
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16. Quorums
•A quorum is “the minimum number of members required to be
present at an assembly or meeting before it can validly proceed to
transact business.”
•A quorum is nothing more than the minimum number of votes
required for a majority.
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17. Quorums
•To put it simply, a quorum is the cluster’s configuration database.
The database resides in a file named MSCSquolog.log.
•The quorum is sometimes also referred to as the quorum log.
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18. Quorums
•What quorums do:
•The job of the quorum in this capacity is to prevent the problem
from happening and essentially decide whether the cluster can or
should continue to function:
•stopping a problematic node’s service until it can communicate
properly with the rest of the clusters.
•When the issue is resolved, the quorum will allow the problematic
node to rejoin the cluster group and restart all the needed
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19. Quorums
•What quorums do:
••The quorum decision is done through votes; each node in a
cluster has a single vote, and the cluster itself can be configured as
a witness vote.
••Quorum in failover clustering has four options
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20. Majority Node
•The Majority Node option is recommended for clusters with an odd
number of nodes.
•This configuration can handle a loss of half of the number of cluster
nodes rounded off downwards. For example, a cluster of five nodes
can handle the failure of two nodes.
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21. Majority Node
•When we have a five nodes cluster, where three of the nodes can
communicate with each other but the last two cannot, the three
nodes have enough votes for a majority and the cluster will remain
active despite the possible failure of two nodes.
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23. No Majority: Disk Only
•This option only requires one active cluster node to keep the
cluster active; the quorum is stored on a disk.
•For that reason, this option is generally not recommended. If all
cluster nodes are healthy, the network has no problems. However
when the disk is no longer available (or becomes corrupted) the
cluster fails.
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24. Node and Disk Majority
•This option is recommended for clusters with an even number of
nodes and provides multiple possibilities there for the maximum
number of nodes that may fail before the cluster goes down.
•This depends on the availability of the disk (also named "Witness
Disk Resource"). Aside from holding a vote, the disk also serves as
storage for the most recent cluster database.
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26. Node and Disk Majority
• This configuration can handle a failure of half the cluster nodes because it
holds an extra vote.
• In a six-node cluster three nodes can fail and the cluster remains online.
• If the disk is not available, this configuration can handle a failure of half the
nodes minus one.
• So the same six-node cluster can handle the failure of two nodes and still
remain online.
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27. Node and File Share Majority
•This configuration is similar to "Node and Disk Majority" but in this
case the disk is replaced by a file share (also called the "File Share
Witness Resource").
•There is one important difference: after the failure of a cluster, one
of the nodes will have a local copy of the most recent cluster
configuration. If that is not present the cluster service must be
started manually.
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28. Summary
The purpose of the clustering are to allows group of nodes to
provide: Highly available, share capacity, Highly visibility, Fault-
tolerance
•Zero down time for any patching or maintenance to cluster nodes
•So on and so far
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