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I have heard that virtualization is the basis of Cloud,so If i have a machine with xen as virtualizing environment and many vms running on it,then can that be called as a cloud.

Is it true that vms that scale based on load and memory is called cloud and vms that do not scale is called as just virtualization!

How can a vm scale??Based on my understanding for xen once we fix cpu and ram,it cant go beyond that (am aware of Dynamic memory Management) so how it really scale?.Can any one please clarify this

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Welcome to Server Fault. Please take a moment to read the FAQ, as well as How can I ask better questions on Server Fault? –  Michael Hampton Sep 12 '12 at 5:49
    
can u please look into it now please....i have changed my question.. –  Echelon Sep 12 '12 at 6:02
    
It's still not a good, on-topic question, and at a fundamental level. –  HopelessN00b Sep 12 '12 at 6:12
    
@HopelessN00b if its fundamental then can you please answer it and then down vote.There can be many serverfault users still not knowing the differences ,this can be helpful for them. –  Echelon Sep 12 '12 at 6:18
    
@Echelon Did what I could... but this is not a teaching site where you go to learn basic concepts, nor am I anything resembling a teacher. –  HopelessN00b Sep 12 '12 at 6:24

4 Answers 4

up vote 5 down vote accepted

Echelon, you're at the 100 ft level and the difference between Virtualization and Cloud Computing is at the 10,000 ft level :)

I'll assume we're talking industry terms and not some Xen marketing speak. Your example is just server virtualization, nothing more. Nothing wrong with that, but virtualization is just one component of the cloud computing model. The cloud concept is not a feature, or specific thing, but a framework for all the things you build and automate around your virtualization.

Microsoft's Young Chou does a great talk on what it takes to "build a Cloud". You can find a 6-part dissection on his blog, as well as some high-level theory on what is cloud.

Specifically, once you have a virtualization infrastructure (multiple hosts for VM's, scalable storage and networking, etc.) Chou says you will need:

  • Self-Service (Limited number of clicks to deploy a new system, high level of OS and server app deployment automation)
  • Resource Pooling (Standardization plus optimization plus systems management)
  • Elasticity (Grow and shrink number of virtual machines based on demand)
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So basically, you have to build your own replica of AWS's core services (at least EC2, S3/EBS, some database (SimpleDB or Dynamo), etc.)? –  Tom Marthenal Sep 12 '12 at 8:48
    
um, no. Again, this isn't about products, but if you want to dive into an example with Microsoft products: Deploy Hyper-V to physical servers, and virtualize your server workloads. Then deploy System Center 2012 products to manage those workloads. Create automation for deployment of new Server VM's based on sysprep images you design. Use SCVMM, Orchestrator, and App Controller to auto scale your services based on demand (e.g. web site gets too many hits, so system center deploys another svr). Use Ops Mgr to monitor everything. SCVMM does optimization of VM placement and self-service. –  Bret Fisher Sep 12 '12 at 12:51
    
Notice with this example all your doing is delivering virtual servers with your users' apps on them (same thing you're doing now) but in a way that's highly automated, managed, monitored, elastic, optimized, and measured. (say that 5 times fast) –  Bret Fisher Sep 12 '12 at 12:58

No. To all of it. The only part that's really even remotely addressable:

The definition of cloud, as it pertains to... what you're talking about:

Cloud computing is the use of computing resources (hardware and software) that are delivered as a service over a network (typically the Internet). The name comes from the use of a cloud-shaped symbol as an abstraction for the complex infrastructure it contains in system diagrams. Cloud computing entrusts remote services with a user's data, software and computation.

The terminology and symbology originated with networking diagrams where unknown, undefined networks beyond the control and scope of the network diagram (typically the internet at large) were diagrammed as a cloud, so its usage with regards to computers is fairly similar. It can, and often does involve virtualization, but you can have physical servers "hosted in the cloud" and even managed by a "cloud service provider" if you wish.

Regarding scaling and virtualization... I don't know, you're just so far off-base that I really don't know where to even begin.

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...so you're saying cloud computing isn't related to the weather??? –  Tom Marthenal Sep 12 '12 at 6:39
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@TomMarthenal I said no such thing. In fact, last big storm we got through here wreaked havoc on our cloud resources due to a combination of general damage to our ISP's network and a massively increased load on cloud providers, as a lot of area businesses had to fire up or fail over to cloud instances, creating a highly unanticipated spike in demand for scarce computing resources. So actually, stormy weather can easily have an impact on cloud computing, and those 51% of people surveyed are right... even if only by complete accident. :) –  HopelessN00b Sep 12 '12 at 7:04

'The Cloud' is a vague term which doesn't require virtualisation of any sort. It simply refers to your data or service residing somewhere out there in the internet in one or multiple places, you don't care where but that it is accessible from anywhere.

Cloud computing is simply computing in the cloud. Again, virtualisation not required, although it is a common example. You can also have apps run as a service eg. Google App Engine

So people have started using the terms of private cloud or their own cloud which is wrong because it is mixing concepts but since when did management speak need to make any sense? This is more than simply virtualisation where you might have hardware dedicated to types of machines and you might present VMs as an online machine to your users, but the idea of setting up a generic platform that is presented to another business role to manage VMs on (although that could be you wearing a different hat) The implication that you can adapt, fire up clones, test machines, change hardware, etc. more easily.

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Virtualization is just one component of the cloud computing model. The cloud concept is not a feature, or specific thing, but a framework for all the things you build and automate around your virtualization.

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This answer could be improved by describing what "all the things you build and automate around your virtualization" are. –  Michael Hampton Jun 30 '13 at 17:39

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