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Cloud is a common term for hiring a services over the Internet. The word cloud comes from the common custom to draw figures that describe communication over the Internet as a cloud, for example on the picture below.


There is one precise definition of the term cloud in the document The NIST Definition of Cloud Computing but it has 2 pages because it contains five essential cloud characteristics, three model of services and four models of deployment.

Deployment schemas are public, private, community and hybrid cloud. It means that services are for a public hire or only in private organisation, in closed community or hybrid way.

The most essential cloud characteristics are: On-demand self-service, Broad network access, Resource pooling, Rapid elasticity a Rapid elasticity.

The hardest to explain are three service models: SaaS, PaaS and IaaS. See examples below.

SaaS - Software as a service

SaaS - Software-as-a-Service - The capability provided to the consumer is to use the provider’s applications running on a cloud infrastructure. The applications are accessible from various client devices through either a thin client interface, such as a web browser (e.g., web-based email), or a program interface. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities

  • web-based email - GMail, Hotmail, Centrum.cz mail, Seznam.cz Email
  • social networks and chatting apps - Facebook, Google+, Twitter
  • online office packages - Google Docs, Microsoft Office 365
  • file sharing - Dropbox, Google Drive, Microsoft OneDrive, ownCloud
  • picture sharing - Picasa, Flickr, Rajce.net
  • music records libraries - Spotify, Google Play, iTunes
  • video libraries - YouTube, Vimeo
  • communication platforms - Adobe Connect, WebEx
  • ERP software - Salesforce, NetSuite
  • CMS software - Google Sites, Wordpress.com

SaaS is sometimes called „software on-demand“ or „Application Service Providing“.

PaaS - Platform as a service

The capability provided to the consumer is to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages, libraries, services, and tools supported by the provider. 3 The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, or storage, but has control over the deployed applications and possibly configuration settings for the application-hosting environment. As example:

  • Google App Engine (supports PHP, Python, Java, Go)
  • Amazon Elastic Beanstalk (supports Ruby, PHP, Python, .NET, Java, JavaScript)
  • Heroku (supports Ruby, PHP, Python, Java, JavaScript, Perl)
  • Microsoft Azure Websites (supports PHP, Python, .NET, JavaScript)
  • Red Hat OpenShift (supports Ruby, Python, PHP, JavaScript, Perl, Java, Haskell, .NET)

IaaS - Infrastructure as a Service

Infrastructure-as-a-Service - The capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, and deployed applications; and possibly limited control of select networking components.

Infrastructure-as-a-Service provides VM - virtual machines containing a complete platform for operating system run. One or more virtual machines can be alocated in one physical device with special virtualization software hypervizor (for example, KVM, Xen, VMware, VirtualBox).

Infrastructure-as-a-Service supports creating and removing their virtual machines freely. It may be done manualy or based on rules like "run another VM, if are current VM utilized on 95% and more".

Well-known examples of public IaaS clouds:

  • Amazon Elastic Compute Cloud
  • Google Compute Engine
  • Microsoft Azure
  • Rackspace Cloud Servers

Private IaaS cloud can be created by following software tools:

  • OpenNebula
  • OpenStack
  • Eucalyptus
  • VMware vCloud Suite

IaaS cloud may be used directly, for example to render cartoons or any other demanding computations or as a layer for PaaS a SaaS cloud.

Cluster types summary

There are three different model of services:

  • Software-as-a-Service enable access to software both as a downloadable code or remotely by program API.
  • Platform-as-a-Service supports software environment to run applications, it involves programming languages and thei libraries.
  • Infrastrucure-as-a-Service enables services of virtual data center (virtual machine, virtual network, virtual data storage, etc.).

Cloud in MetaCentrum

Metacentrum run community IaaS cloud for demanding computations. See Cloud v MetaCentru.

CESNET also run these SaaS services:

MetaCloud is an IaaS (Infrastructure as a Service) cloud built using OpenNebula v4.10. Pilot cloud installation provided by CESNET and CERIT-SC.

MetaCloud is similar to e.g. Amazon Elastic Compute Cloud (EC2) or Google Compute Engine. MetaCloud is partially compatible with Amazon EC2.

clouds compared
MetaCloud Amazon EC2 Google Compute Engine
web interface URL https://cloud.metacentrum.cz/ https://console.aws.amazon.com/ec2/ https://console.developers.google.com/
hypervisors KVM Xen KVM
provided disk images Debian, CentOS, SciLinux, MS Windows Amazon Linux, Ubuntu, RedHat, Suse, MS Windows Debian, RHEL, CentOS, SLES
disk image upload formats qcow2, vmdk, vdi, raw raw disk.raw in tar.gz
term for VM VM instance instance
term for VM spec (CPUs,RAM..) template AIM + instance type image + machine type
terms for VM suspend, stop and delete suspend, stop, undeploy -, stop, terminate -, -, delete
file storage service Cumulus (S3 compatible) S3 Google Cloud Storage
persistent disk storage persistent disk images, copy on start and stop Elastic Block Store, mounted over network persistent disk images

Practical information (how to start)

  1. Registration
  2. Quick guide
  3. MetaCloud usage examples
  4. Changing your MetaCloud password

Basic information about service and used technology

Hardware resources

  • 10 x 24 cores (Intel Xeon), 10 x 96GB RAM
  • 8 x 12 cores (Intel E5-2620, CERIT-SC), 8 x 90 GB RAM
  • 44TB available shared storage

Who is eligible to use this service

Two pilot installations are available for early adopters:

What we provide

  • You can create virtual machines from linux based images (Metacentrum's or yours, Microsoft supported partially due to license issues)
  • Image and data storage (Shared FS, Amazon S3, GridFTP)
  • Virtual machine managment (Web GUI or command line)
  • Support and help