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Cloud Computing
Part 1
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Introduction to Cloud Computing
(a) Introduction
- Plugging an electric appliance into an outlet
* We care neither how electric power is generated nor how it gets to that outlet
* Electricity is virtualized
→ It is readily available from a wall socket that hides power generation stations and a huge
distribution grid
* Extending to information technology (IT): delivering useful functions while hiding how their
internals work
→ Computing is virtualized and must allow computers to be built from distributed
components such as processing, storage, data, and software resource

- Basic concept of cloud computing
→ Allowing access to large amounts of computing power in a fully virtualized manner,
including computing, storage, and software
* Resources are aggregated and offered in a single system view
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* On-demand delivery of computing power: utility computing
→ Similar to traditional public utility services such as water, electricity, gas, and telephony
* Technologies: cluster, grid, and cloud computing

- Definitions of cloud computing
* Buyya et al
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:
Clouds are a large pool of easily usable and accessible virtualized resources (such as
hardware, development platforms and/or services)
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This pool of resources is typically exploited by a pay-per-use model in which
guarantees are offered by the Infrastructure Provider by means of customized Service Level
Agreements
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C
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g
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:
Data center hardware and software that provide services
* Sotomayor et al
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0
* Distributed computing: clusters, grids
* Systems management: autonomic computing, data center automation

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- New computing models emerge
* A century ago, companies used to generate their own electric power
→ However, it’s cheaper just plugging their machines into the electric power grid
* Computing power used to be generated in-house
→ However, it’s cheaper to use utility-supplied computing resources delivered over the
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Internet as Web services
# Reduction on IT-related costs and less personnel hiring
# Providers of IT services achieve better operational costs: high usage rate for serving more
customers
* Definition of computing delivered as a utility
# On demand delivery of infrastructure, applications, and business processes in a securityrich, shared, scalable, and based computer environment over the Internet

- Web services (WS): services that are made available from a business’s Web server for
Web users or other Web-connected programs
* Glue together applications running on different plat-forms
* Enable information from one application to be available to others
* Enable internal applications to be available over the Internet
* Main technologies: HTTP and XML

- Service-oriented architecture (SOA): a software design and software architecture
design pattern
* Service-orientation: an application’s functionality is provided as services to other applications
* Each service implements one action and uses defined protocols that describe how services
pass and parse messages using description metadata
* Loosely coupled, standards-based, and protocol-independent distributed computing
* SOA aims to allow users to string together fairly large chunks of functionality to form ad hoc
applications that are built almost entirely from existing software services
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* Software resources are packaged as “services” that
# are well-defined, self-contained modules that provide standard business functionality
# are independent of the state or context of other services → loosely coupled
# follow industry standards, such as HTTP, XML, SOAP, …
* Development, maintenance, and usage of the SOA
# Reuse, granularity, modularity, composability, componentization, and interoperability
# Standards-compliance (both common and industry-specific)
# Services identification and categorization, provisioning and delivery, and monitoring and
tracking

- Web 2
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g
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icio
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and services, e
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, Facebook like, Google map, Google+,
subscription,
...
, and in general
managed as a single virtual system
...
g
...
g
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g
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* Hardware virtualization allows running multiple operating systems and software stacks on a
single physical platform (See the figure below)
* Virtual machine monitor (VMM, also called a hypervisor), mediates access to the physical
hardware and provides each guest operating system with a virtual machine (VM)
* New technologies, such as multi-core chips, paravirtualization, hardware-assisted
virtualization, live migration of VM, etc
...
g
...
com, Google App Engine, Heroku, Cloud Foundry, Microsoft Azure, …

- Iaas
* Provides on-demand provisioning of servers running several choices of operating systems and
a customized software stack
* Offers virtual resources on demand: computation, storage, and communication
* Bottom layer of cloud computing systems
* Example: Amazon EC2, Google Compute Engine, Rackspace, GoGrid, Microsoft, HP, AT&T,
OpSource, …
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# Offers VMs with a software stack that can be customized
# Users may perform activities to the server: starting and stopping it, customizing it by
installing software packages, attaching virtual disks to it, and configuring access
permissions and firewalls rules

- Deployment models of cloud services: public, private, community, or hybrid

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* Public cloud: cloud made available in a pay-as-you-go manner to the general public
* Private cloud: internal data center of a business or other organization, not made available to
the general public
* Community cloud: shared by several organizations and supports a specific community that has
shared concerns (e
...
, mission, security requirements, policy, and compliance considerations)
* Hybrid cloud: a private cloud supplemented with computing capacity from public clouds

(d) Desired feature of a cloud
- Desired features
* Self-service
# Cloud users expect on-demand and nearly instant access to resource
# Hence, self-service allow customers to request, customize, pay, and use services without
intervention of human operators
* Per-usage metering and billing
# Services must be priced on a short- term basis (e
...
, by the hour) and allow users to release
resources as soon as they are not needed
# Allow efficient trading of service such as pricing, accounting, and billing
* Elasticity
# Cloud computing gives the illusion of infinite computing resources available on demand
# Additional resources can be provisioned when an application load increases, and released
when load decreases (i
...
, scale up and down)
* Customization
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# Resources rented from the cloud must be highly customizable
# For IaaS: allow users to deploy specialized virtual appliances and grant root access to the
virtual servers
# For PaaS and SaaS: less flexibility and not suitable for general-purpose computing, but still
expected to provide a certain level of customization

(e) Cloud infrastructure management
- Cloud infrastructure management
* Managing physical and virtual resources: servers, storage, and networks
* Provision resources to applications rapidly and dynamically
* Also called “cloud operating system,” “infrastructure sharing software,” and “virtual infrastructure engine”
* Virtual infrastructure manager (VIM)
# Responsible for cloud infrastructure management
# Resembles a traditional operating system, but instead of dealing with a single computer, it
aggregates resources from multiple computers, presenting a uniform view

- Features of VIM
* Virtualization support
# Virtualized resources (CPUs, memory, etc
...
g
...
g
...
g
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amazon
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NET
# Heroku: Ruby
# Force
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NET, …
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* Databases (DB)
# Traditional DB: relational DB
- Offers reliable structured data storage and transaction processing
- Lacks scalability to handle several petabytes of data
# Cloud DB
- Highly distributed
- Robust and highly scalable, at the expense of relational structure and convenient query
languages
# Examples: Amazon SimpleDB and Google App Engine datastore
- Schema-less and automatically indexed database
- Data queries can be performed only on individual tables; that is, join operations are
unsupported for the sake of scalability

- Examples

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(h) Challenges and risks
- Security, privacy, and trust
* Cloud s are essentially public: the system is exposed to more attacks
* Cloud providers may locate the data anywhere on the planet
# Specific cryptography techniques may not be allowed in some countries
* The trust toward providers is fundamental to ensure the desired level of privacy

- Data lock-in and standardization
* Current cloud computing infrastructures and platforms do not employ standard methods of
storing user data and applications
# Data cannot be easily moved out of a certain cloud provider: data lock-in
* Standardization
# Cloud Computing Interoperability Forum (CCIF)
- Formed by organizations such as Intel, Sun, and Cisco
- Enables a global cloud computing ecosystem whereby organizations are able to seamlessly
work together for the purposes for wider industry adoption of cloud computing technology
- Unified Cloud Interface (UCI): aims at creating a standard programmatic point of access
to an entire cloud infrastructure
# Open Virtual Format (OVF)
- Facilitates packing and distribution of software to be run on VMs so that virtual
appliances can be made portable
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- Availability, fault-tolerance, and disaster recovery
* Cloud user expectations: availability of the service, its overall performance, and measures to
be taken when something goes wrong in the system or its components
* SLAs, which include QoS requirements, must be ideally set up between customers and cloud
providers to act as warranty

- Resource management and energy-efficiency
* Efficient management of virtualized resource pools: CPUs, disk space, and network
bandwidth must be sliced and shared among virtual machines effectively and efficiently
* Migration of VMs: trade-off between the negative impact of a live migration on the
performance and stability of a service and the benefits to be achieved with that migration
* Data centers impact the environment
# Consume and generate large amounts of electricity and heat
# Emit CO2 from the cooling system

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