Cloud Computing Basics

Hi

going to write a good article on cloud computing in detail

http://www.youtube.com/watch?v=QYzJl0Zrc4M

Cloud computing is separating your application from hardware and operating system.That the reason we say the application is on the cloud.

So the simple question in anyones mind is how was the application stored earlier.Even earlier it was stored on a server machine(any

computer which acts as server).So suppose you are owner of IT company and you have software installed on your machine and the client

accesses it from web browser so will they say application is on the cloud.No.

So why not.The application is still dependent on your hardware and operating system.Your server has windows server edition and some

hardware RAM, hard drive so if your windows crashes then the application is gone even if your hard drive crashes teh application is

gone.So its not on the cloud

With the coming of virtual machine cloud computing became possible.Virtulization software like XEN make it possible for

virutalization. so you have one server( any PC)  on that instead of windows you have XEN there is one more PC which acts as your XEN

Master machine which know the status of your server.

So suppose your server fails it will migrate the application to other server which now how it does it(Eg ESXI (slave) and Vsphere

(Management softwaer on other machine).Basically when you install any virtualization software it installs operating system on that

software so basically its like a file sitting on that software it can directly copy paste that file.That is you can migrate a OS

directly like a music file.

If you want to install ubuntu on your machine then install VMplayer(Virtualization software) first and it it you can have a ubuntu

virtual machine.

before we had virtualization suppose we wanted to migrate a application from one server to other we needed to take backup of

application , install windowns on another server and then install that aplication on windowns and then migrate the application data

which would take atlesas a day

Now you have hypervisor and application like Vsphere which acts as master to these machines on which hypervisor are installed.If you

need details about vsphere read below

vSphere HA provides high availability for virtual machines by pooling the virtual machines and the hosts they reside on into a

cluster. Hosts in the cluster are monitored and in the event of a failure, the virtual machines on a failed host are restarted on

alternate hosts.

When you create a vSphere HA cluster, a single host is automatically elected as the master host. The master host communicates with

vCenter Server and monitors the state of all protected virtual machines and of the slave hosts. Different types of host failures are

possible, and the master host must detect and appropriately deal with the failure. The master host must distinguish between a failed

host and one that is in a network partition or that has become network isolated. The master host uses datastore heartbeating to

determine the type of failure.To check in depth of how clustors work.Check the link at the end of this article

Types of virtualization

client installed means we have a operating system installed on top of that we are installing a virtualization software(Eg vmware

fusion)

Hypervisor

ESXI - hypervisor from vmware .you install ESXI for this no need to install windows.It acts like a operating system

so we install the hypervisor on server(No OS installed before this step).For this you need a management software .Vsphere is a

managmenet software.EXSI is called bare metal hypervisor as it does not require any OS to run on.It has its own kernel.Some

background here.The intial kernel the program that control your hardware like RAM, hard drive were writen by unix (some scientists in

bell labs).These were used by linux which came much later and i guess to some extent by windows. so ESXI also uses them.

Wiki links

http://en.wikipedia.org/wiki/VMware_ESX

why hypervisor are powerful.

consider we have 3 physical server and we install EXSI on each of those 3 server.suppose a powersupply fails on one server it

transfers the OS with application to next server for fault tolerance this is amazing as no need to maintain redundancy like in raid

Virtualization alllows you to move entire OS from one server to other like copy paste.

So What are Amazon and Microsoft advertising for ??

so instead of buying server hardware now you can buy a instance(virtual machine).

Going into more detail like speed and bandwidth for these VM

in case of amazon edge servers there is a one central server and there are 9 servers located through US which will make it easier for

people to watch content fast.Now since they charge per usage that is how much users are using your site then in this case you need to

pay for transfter to edge server from central server and then to user computer from edger server so if you have users across country

accssing your site you need to pay for transfters to each edge servers.apart from this consider a video depending on the speed of

user there are different version of vid that central server transfters to edge server suppose user strats with 10mbps speed and then

the speed reduces to 500kb because of net issues then the first time the central server will transfer 1gb file then at the other time

it will transfter 500mb file so you are charged double

virtual iron a virtulization software can turn on physical server and turn off as needed

Things to consider

with cloud servers a lot of data goes in and out so need to worry aobu the speed of internet.but the problem with hosted exchange and

other things with cloud is the amount of time it takes to put the stuff on the internet

public v/s private clouds

Public clouds

microsfost azure ..

elastic cloud computing

edge server for amazon

Private clouds

Cloud hosted inside your company are private clouds

Now cloud computing is more than just virtulization

Some technologies before clouds

Initially there were mainframes that is there were dummy terminals (computers which did not have much processing power) which are

then connected to mainframes(big machines with processing power) so every thing you do is actually done by the mainframe server.These

were called terminal services.

Citrix MetaFrame allows you to run application from windows terminal servers ..example using citrix to run datastage

terminal services are now called remote desktop services

Then came the client server model that is software was installed on client (PC which had computing power) then connected to server

but it had its drawbacks like update to client software would take time.

The came the 3 tier architecture that the your bank login that you are accessing from home

How virtual host clustor works

http://www2.isupportyou.net/2010/07/what-is-clustering-how-it-works.html

www.youtube.com/watch?v=-NY_N_oyW4Y

Search for VMware vSphere Platform Overview videos

http://www.vmware.com/products/datacenter-virtualization/vcloud-suite/how-it-works.html

Apart from these videos there are number of vsphere resources out there.Its a big topic like how replication takes place.My idea in

this article was to give you a brief idea about virtulization.Get the highlevel of it.