The document discusses high availability (HA) clustering which uses multiple computers to minimize downtime for server applications. It describes different types of HA clustering including connectivity-based, centroid-based, distribution-based, and density-based clustering. Specific examples of implementing HA are also provided for DNS, VMs, DHCP, SQL, domains, storage, web applications, file servers, and networks.

1. ASSIGNMENT ON
HIGH AVAILABILITY (CLUSTERING)
PREPARED BY: MD. SHIHAB HOSSAIN

2. WHAT IS HIGH AVAILABILITY?
• High-availability clusters (also known as HA clusters or fail-
over clusters) are groups of computers that support server
applications that can be reliably utilized with a minimum
amount of down-time.

3. TYPES OF HIGH AVAILABILITY
• Connectivity-based clustering (hierarchical clustering)
• Centroid-based clustering
• Distribution-based clustering
• Density-based clustering

4. CONNECTIVITY-BASED CLUSTERING
(HIERARCHICAL CLUSTERING)
• Connectivity based clustering, also known as hierarchical
clustering, is based on the core idea of objects being more
related to nearby objects than to objects farther away.

5. CENTROID-BASED CLUSTERING
• In centroid-based clustering, clusters are represented by a
central vector, which may not necessarily be a member of the
data set. When the number of clusters is fixed to k, k-means
clustering gives a formal definition as an optimization problem:
find the k cluster centers and assign the objects to the nearest
cluster center, such that the squared distances from the cluster
are minimized.

6. DISTRIBUTION-BASED CLUSTERING
• The clustering model most closely related to statistics is based
on distribution models. Clusters can then easily be defined as
objects belonging most likely to the same distribution.

7. DENSITY-BASED CLUSTERING
• In density-based clustering, clusters are defined as areas of
higher density than the remainder of the data set. Objects in
these sparse areas - that are required to separate clusters - are
usually considered to be noise and border points

8. HIGH AVAILABILITY ON DNS
TO PROVIDE A HIGH-AVAILABILITY TO OUR DNS SERVERS, WE WILL CONFIGURE TWO
SERVERS. ONE SERVER WILL ACT AS THE PRIMARY ONE WHEREAS THE OTHER WILL ACT
AS THE SECONDARY ONE. THE GOAL IS TO ENSURE THE CONTINUITY OF OUR DNS
SERVICE IF ONE SERVER CRASH

9. HIGH AVAILABILITY ON VM
• Enabled by a server cluster, high availability is a hypervisor
feature that limits downtime when a virtual machine (VM) fails.
VMware vSphere, Microsoft Hyper-V and Citrix XenServer offer
high-availability features to ease disaster recovery in virtual
infrastructures

10. HIGH AVAILABILITY ON DHCP
ENSURING HIGH AVAILABILITY OF CRITICAL NETWORK SERVICES LIKE DHCP FIGURES
HIGH IN THE LIST OF PRIORITIES FOR ANY ENTERPRISE. IN AN ENVIRONMENT WHERE
CLIENTS GET THEIR IP ADDRESSES AND NETWORK CONFIGURATION AUTOMATICALLY,
UNINTERRUPTED NETWORK CONNECTIVITY IS DEPENDENT ON THE AVAILABILITY OF
DHCP

11. HIGH AVAILABILITY ON SQL
THIS TOPIC INTRODUCES SEVERAL SQL SERVER HIGH-AVAILABILITY SOLUTIONS
THAT IMPROVE THE AVAILABILITY OF SERVERS OR DATABASES. A HIGH-
AVAILABILITY SOLUTION MASKS THE EFFECTS OF A HARDWARE OR SOFTWARE
FAILURE AND MAINTAINS THE AVAILABILITY OF APPLICATIONS SO THAT THE
PERCEIVED DOWNTIME FOR USERS IS MINIMIZED.

12. HIGH AVAILABILITY ON DOMAIN
MULTI-DOMAIN SERVER HIGH AVAILABILITY - MULTIPLE MULTI-DOMAIN SERVERS ARE,
BY DEFAULT, AUTOMATICALLY SYNCHRONIZED WITH EACH OTHER.

13. HIGH AVAILABILITY ON STORAGE
HIGH-AVAILABILITY STORAGE (HA STORAGE) IS A STORAGE SYSTEM THAT IS
CONTINUOUSLY OPERATIONAL OR PROVIDES AT LEAST 99% UPTIME.

14. HIGH AVAILABILITY ON WEB
CONFIGURING HIGH AVAILABILITY FOR WEB TIER COMPONENTS THAT RECEIVES EACH
INCOMING HTTP REQUEST AND INVOKES THE REQUESTED BUSINESS LOGIC OPERATION
IN THE APPLICATION. BASED ON THE RESULTS OF THE OPERATION AND STATE OF THE
MODEL, THE NEXT VIEW IS SELECTED TO DISPLAY

15. HIGH AVAILABILITY ON FILE SERVER
A CLUSTERED FILE SYSTEM IS A FILE SYSTEM WHICH IS SHARED BY BEING
SIMULTANEOUSLY MOUNTED ON MULTIPLE SERVERS. THERE ARE SEVERAL
APPROACHES TO CLUSTERING, MOST OF WHICH DO NOT EMPLOY A
CLUSTERED FILE SYSTEM (ONLY DIRECT ATTACHED STORAGE FOR EACH
NODE).

16. HIGH AVAILABILITY ON NETWORK
HIGH-AVAILABILITY ROUTING SYSTEMS ARE A GROWING REQUIREMENT,
PARTICULARLY AT THE NETWORK EDGE WHERE CIRCUITS ARE TERMINATED
AND REROUTING AROUND A FAILED DEVICE IS OFTEN NOT AN OPTION