Transcript Unit-1-Concepts-Introduction

Distributed & Cloud Computing
Course Instructor: Babu Ram Dawadi
Unit 1: Introduction.
10 Hrs
Understanding distributed system and its goals, Hardware, Software concepts
and design issues of distributed system, Concepts of cloud computing, Cloud
Architecture, SAAS, PAAS, IAAS and others, Organizational Scenarios of
Clouds, Types of Clouds: Private, Public & Hybrid, Comparing the various cloud
architectures, Benefits and Limitations of Clouds, Challenges of Cloud
Computing.
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Defining Distributed Systems
 Various definition of distributed systems
have been given in the literature, for
example:
 A collection of logically related data that is
distributed over different processing nodes
of computer network.
 Definition above does not provide all
characteristics of distributed systems.
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Defining Distributed Systems
 It is difficult to find a definition that provides all
characteristics of distributed systems.
 Another way is a definition that gives a loose
characterization for distributed systems such as:
 A distributed system is a collection of independent
computers that appear to the users of the system
as a single computer.
 With any definition, sharing of resources is a
main motivation for constructing distributed
systems.
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Defining Distributed Systems
 In this course, we define distributed
systems more precisely as :
 A distributed system is one in which
hardware or software components located
at networked computers communicate and
coordinate their actions only by message
passing.
 Definition above covers the entire range of
distributed systems in which networked
computers can usefully be deployed.
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Defining Distributed Systems
 Networks of computers are everywhere!
 Examples of networks of computers are:
 Mobile phone networks
 Corporate networks
 Factory networks
 Campus networks
 Home networks
 In-car networks
 On board networks in aero planes and
trains
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Defining Distributed Systems
 Our definition of distributed systems has
the following significant consequences:
 Concurrency
 Tasks carry out independently
 No global clock
 Tasks coordinate their actions by
exchanging messages
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Defining Distributed Systems
 Independent Failures
 Faults in the network result in the isolation
of the computers that are connected to it.
 Each component of the system can fail
independently, leaving the others still
running.
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Design Challenges of Distributed Systems

Designers of distributed systems need to
take the following challenges into account:
 Heterogeneity
 Heterogeneous components must be able
to interoperate.
 Openness
 Interfaces should allow components to be
added or replaced.
 Security
 The system should only be used in the way
intended.
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Design Challenges of Distributed Systems
 Scalability
 System should work efficiently with an
increasing number of users.
 System performance should increase with
inclusion of additional resources.
 Failure handling
 Failure of a component (partial failure)
should not result in failure of the whole
system.
 Transparency
 Distribution should be hidden from the user
as much as possible.
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Heterogeneity
 Heterogeneous components that must be
able to interoperate, apply to all of the
following:
 Networks
 Hardware architectures
 Operating systems
 Programming languages
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Heterogeneity
 Examples that mask differences in
network, operating systems, hardware and
software to provide heterogeneity are
 Middleware
 Internet protocols
 Mobile code
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CHARACTERIZATION OF DISTRIBUTED SYSTEMS
Heterogeneity
 Middleware
 Middleware applies to a software layer.
 Middleware provides a programming
abstraction.
 Middleware masks the heterogeneity of the
underlying networks, hardware, operating
systems and programming languages.
 The Common Object Request Broker
(CORBA) is a middleware example.
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Heterogeneity
 Mobile code
 Mobile code is the code that can be sent
from one computer to another and run at the
destination.
 Java applets are the example of mobile
codes.
 Virtual machine/Container
 Virtual machine provides a way of making
code executable on any hardware.
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Openness
 Distributed systems must be extensible.
 Openness of a computer system is the
characteristic that determines whether the
system can be extended and re-implemented in
various ways.
 The first step in openness is publishing the
documentation of software components and
interfaces of the components to make them
available to software developers
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Security
 Security of a computer system is the
characteristic that the resources are
accessible to authorized users and used in
the way they are intended.
 Security for information resources has
three components:
 Confidentiality
 Protection against disclosure to
unauthorized individual.
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Security
 Integrity
 Protection against alteration or corruption.
 Authenticity
 Protection against interference with the
means to access the resources.
 Security Mechanisms are:
 Encryption
 Authentication
 Authorization
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Scalability
 Scalable distributed systems operate
effectively and efficiently at many different
scales, ranging from a small Intranet to the
Internet.
 Scalable distributed systems remain
effective when there is a significant
increase in the number of resources and
the number of users.
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Scalability
 Challenges of designing scalable
distributed systems are:
 Controlling the cost of physical resources
 Cost should linearly increase with the
system size.
 Controlling the performance loss
 For example, in hierarchically structured
data, search performance loss due to data
growth should not be beyond O(log n),
where n is the size of data.
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Scalability
 Preventing software resources running out
 An example is the numbers used as Internet
addresses (IP)(32 bit->128-bit)
 Y2K like problem.
 Avoiding performance bottlenecks
 Using decentralized algorithms to avoid
having performance bottlenecks.
 Caching and replication in Web are
examples of providing scalability.
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Failure handling
 Failures in distributed systems are partial,
that is some components fail while others
continue to function.
 Techniques for dealing with failures:
 Detecting failures
 E.g. Checksums
 Masking failures
 E.g. Retransmission of corrupt messages
 E.g. File redundancy
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Failure handling
 Tolerating failures
 E.g. Exception handling
 E.g. Timeouts
 Recovery from Failure
 E.g. Rollback mechanisms
 Redundancy
 E.g. Redundant components
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Concurrency
 With concurrency, services and applications can
be shared by clients in a distributed system.
 For an object to be safe in a concurrent
environment, its operations must be
synchronized in such a way that its data remains
consistent.
 Concurrency can be achieved by standard
techniques such as semaphores, which are used
in most operating systems.
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Transparency
 Transparency is defined as the hiding of
the separation of components in a
distributed systems from the user and the
application programmer.
 With transparency the system is perceived
as a whole rather than a collection of
independent components.
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Transparency
 Forms of transparencies:
 Access transparency
 Enables local and remote resources to be
accessed using identical operations.
 Location transparency
 Enables resources to be accessed without
knowledge of their physical or network
location (for example, which building or IP
address).
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Transparency
 Concurrency transparency
 Enables several processes to operate
concurrently using shared resources without
interference between them.
 Replication transparency
 Enables multiple instances of resources to
be used to increase reliability and
performance without knowledge of the
replicas by users or application
programmers.
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Transparency
 Failure transparency
 Enables the concealment of faults, allowing
users and application programs to complete
their tasks despite the failure of hardware or
software components.
 Mobility transparency
 Allows the movement of resources and
clients within a system without affecting the
operation of users or programs.
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Transparency
 Performance transparency
 Allows the system to be reconfigured to
improve performance as loads vary.
 Scaling transparency
 Allows the system and applications to
expand in scale without change to the
system structure or the application
algorithms.
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Cloud Computing Overview
Credit: http://ntcap.nic.in/Cloudarc01.ppt, Mark Baker
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What is Cloud Computing?
 Cloud Computing is a general term used to describe a new class of
network based computing that takes place over the Internet,
 basically a step on from Utility Computing
 a collection/group of integrated and networked hardware, software
and Internet infrastructure (called a platform).
 Using the Internet for communication and transport provides
hardware, software and networking services to clients
 These platforms hide the complexity and details of the underlying
infrastructure from users and applications by providing very simple
graphical interface or API (Applications Programming Interface).
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What is Cloud Computing?
 In addition, the platform provides on demand
services, that are always on, anywhere, anytime
and any place.
 Pay for use and as needed, elastic
 scale up and down in capacity and functionalities
 The hardware and software services are
available to
 general public, enterprises, corporations and
businesses markets
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Cloud Computing…
 High performance networks and advanced
development of internet is the basis for cloud
computing .
 Cloud computing has started taking shape
incorporating virtualization and on demand
deployment and internet delivery of services.
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Cloud Computing…
 Cloud is a pool of virtualized computer resources
networked, which can:
 Host a variety of workloads.
 Batch-style back-end jobs.
 Interactive user-facing applications.
 Workloads can be deployed and scaled out quickly through the
rapid provisioning of virtual machines or physical machines.
 Support redundant, self recovering, highly scalable programming
models that allow workloads to recover from many
unavoidable hardware / software failures.
 Monitor resource use in real time to enable rebalancing of
allocations when needed.
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Cloud Computing…
 Cloud computing is an umbrella term used to refer to
Internet based development and services
 A number of characteristics define cloud data,
applications services and infrastructure:
 Remotely hosted: Services or data are hosted on remote
infrastructure.
 Ubiquitous: Services or data are available from anywhere.
 Commoditized: The result is a utility computing model similar to
traditional that of traditional utilities, like gas and electricity - you
pay for what you would want!
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Conventional Computing
vs.
Cloud Computing
Cloud
Conventional





Manually Provisioned
Dedicated Hardware
Fixed Capacity
Pay for Capacity
Capital & Operational
Expenses





Self-provisioned
Shared Hardware
Elastic Capacity
Pay for Use
Operational
Expenses
Basic Cloud Characteristics
 The “no-need-to-know” in terms of the underlying
details of infrastructure, applications interface with the
infrastructure via the APIs.
 The “flexibility and elasticity” allows these systems to
scale up and down at will
 utilising the resources of all kinds
 CPU, storage, server capacity, load balancing, and databases
 The “pay as much as used and needed” type of utility
computing and the “always on!, anywhere and any
place” type of network-based computing.
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Basic Cloud Characteristics
 Clouds are transparent to users and
applications, they can be built in multiple ways
 branded products, proprietary open source, hardware
or software, or just off-the-shelf PCs.
 In general, they are built on clusters of PC
servers and off-the-shelf components plus Open
Source software combined with in-house
applications and/or system software.
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Cloud Computing Characteristics
Common Characteristics:
Massive Scale
Resilient Computing
Homogeneity
Geographic Distribution
Virtualization
Service Orientation
Low Cost Software
Advanced Security
Essential Characteristics:
On Demand Self-Service
Broad Network Access
Scalable and Elastic
Shared/Pool Resources
Metered by Use
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Adopted from: Effectively and Securely Using the Cloud Computing Paradigm by peter Mell, Tim Grance
Shared / Pooled Resources:
 Resources are drawn from a common pool
 Common resources build economies of scale
 Common infrastructure runs at high efficiency
Broad Network Access:
 Open standards and APIs
 Almost always IP, HTTP, and REST
 Available from anywhere with an internet
connection
On-Demand Self-Service:




Completely automated
Users abstracted from the implementation
Near real-time delivery (seconds or minutes)
Services accessed through a self-serve web
interface
Scalable and Elastic:
 Resources dynamically-allocated between users
 Additional resources dynamically-released when
needed
 Fully automated
Metered by Use:
 Services are metered, like a utility
 Users pay only for services used
 Services can be cancelled at any time
Architecture Overview
Cloud Architecture
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Architectural Layers of Cloud Computing
In the cloud computing stack, there are three
basic layers
that together create cloud environment. They are:
1.Infrastructure as a Service(IaaS)
2.Platform as a Service (PaaS)
3.Software as a Service (SaaS)
SaaS
PaaS
IaaS
Service Delivery Model Examples
Amazon
Google
Microsoft
Salesforce
SaaS
PaaS
IaaS
Products and companies shown for illustrative purposes only and should not be construed as
an endorsement
Framework of cloud computing
Application
Services and built in functionality
Developments tools
Platform
Basic middleware
(database services , application server
)
Virtualized resources
Infrastructure
Compute
Networking
Virtualized images
Image Metadata
Storage
Image
Software kernel (OS. VM Manager)
Hardware
Virtual infrastructure management and
Cloud Computing
For building the cloud environment a variety of
requirements must be met to provide a uniform and
homogeneous view of the virtualized resources.
Virtual Infrastructure Management is the key component
to build the cloud environment which does the dynamic
orchestration of virtual machines on a pool of physical
resources.
Virtual infrastructure management provide primitives to
schedule and manage VMs across multiple physical hosts
Cloud management provide remote and secure
interface for creating controlling and monitoring virtualized
resources on IaaS
View of Cloud Deployment
Cloud
Applicatio
n
Client
Infrastructure
SaaS
Application
PaaS
Platfor
m
IaaS
Storag
e
Infrastructure
Virtualized
Application
Service
Software as a Service
 It is a Deployment/Delivery model
• Hosted and managed by vendor
• Delivered across the internet
 It is a Business Model : usage-based pricing (vs. perpetual
license model of on –premise software).Examples:
• Per user per month
• Per transaction
• Per GB of storage per month
Architectural
 Multi-tenancy
 Scalability
 Security
 Performance
Functional
 Provisioning
 Billing
 Metering
 Monitoring
MULTI-TENANCY
 Multi-tenancy is an architectural pattern
 A single instance of the software is run on the
service provider’s infrastructure
 Multiple tenants access the same instance.
 In contrast to the multi-user model, multi-tenancy
requires customizing the single instance according to
the multi-faceted requirements of many tenants.
MULTI-TENANCY
A Multi-tenants application lets customers (tenants) share
the same hardware resources, by offering them one shared
application and database instance ,while allowing them to
configure the application to fit there needs as if it runs on
dedicated environment.
These definition focus on what we believe to be the key
aspects of multi tenancy:
1.The ability of the application to share hardware resources.
2.The offering of a high degree of configurability of the
software.
3.The architectural approach in which the tenants make use
of a single application and database instance.
Multi-tenants Deployment Modes for
Application Server
Fully isolated Application server
Each tenant accesses an application server
running on a dedicated servers.
Virtualized Application Server
Each tenant accesses a dedicated
application running on a separate virtual
machine.
Shared Virtual Server
Each tenant accesses a dedicated
application server running on a shared
virtual machine.
Shared Application Server
The tenant shared the application server
and access application resources through
separate session or threads.
Application Server
Tenant A
Tenant B
Application server
Application server
Tenant A
Virtual
machine
Tenant B
Virtual
machine
Application server
Tenant A
Virtual
machine
Tenant B
Session thread
Tenant A
Application Server
Tenant B
Session Thread
Conceptual framework of Software as a Service
Presentation
Menu and Navigation
User Controls
Display and Rendering
Application
Engine
Security
Reporting
Operation
Identity and federation
User Profile
Workflow
Monitoring and Altering
Authentication and
Single Sign on
Notification and
Subscription
Execution
Handling
Backup and Restore
Authorization and
Role-based Access
Control
Metadata
Execution
Engine
Entitlement
Metadata
Services
Encryption
Messaging
Orchestration
Provisioning
Configuration and
Customization
Data
Synchronization
Performance and
Availability
Metering and Indicators
Regularity Controls
Infrastructure
Database
Storage
Computer
Networking and
Communications
Cloud Service Models
Software as a
Service (SaaS)
Platform as a
Service (PaaS)
SalesForce
CRM
LotusLive
Google
App
Engine
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Adopted from: Effectively and Securely Using the Cloud Computing Paradigm by peter Mell, Tim Grance
Infrastructure as a
Service (IaaS)
SaaS Maturity Model
Level 1: Ad-Hoc/Custom –
One Instance per customer
Level 2: Configurable per
customer
Level 3: configurable &
Multi-Tenant-Efficient
Level 4: Scalable,
Configurable & MultiTenant-Efficient
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Source: Frederick Chong and Gianpaolo Carraro, “Architectures Strategies for Catching the Long Tail”
Different Cloud Computing Layers
Application Service
(SaaS)
MS Live/ExchangeLabs, IBM,
Google Apps; Salesforce.com
Quicken Online, Zoho, Cisco
Application Platform
Google App Engine, Mosso,
Force.com, Engine Yard,
Facebook, Heroku, AWS
Server Platform
3Tera, EC2, SliceHost,
GoGrid, RightScale, Linode
Storage Platform
Amazon S3, Dell, Apple, ...
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Cloud Computing Service Layers
Services
Services
Application
Focused
Services – Complete business services such as
PayPal, OpenID, OAuth, Google Maps, Alexa
Application
Application – Cloud based software that eliminates
the need for local installation such as Google Apps,
Microsoft Online
Development
Development – Software development platforms used
to build custom cloud based applications (PAAS &
SAAS) such as SalesForce
Platform
Infrastructure
Focused
Description
Storage
Hosting
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Platform – Cloud based platforms, typically provided
using virtualization, such as Amazon ECC, Sun Grid
Storage – Data storage or cloud based NAS such as
CTERA, iDisk, CloudNAS
Hosting – Physical data centers such as those run by
IBM, HP, NaviSite, etc.
Software as a Service (SaaS)
 SaaS is a model of software deployment where
an application is hosted as a service provided to
customers across the Internet.
 Saas alleviates the burden of software
maintenance/support
 but users relinquish control over software versions
and requirements.
 Terms that are used in this sphere include
 Platform as a Service (PaaS) and
 Infrastructure as a Service (IaaS)
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Virtualization
 Virtual workspaces:
 An abstraction of an execution environment that can be made
dynamically available to authorized clients by using well-defined
protocols,
 Resource quota (e.g. CPU, memory share),
 Software configuration (e.g. O/S, provided services).
 Implement on Virtual Machines (VMs):
 Abstraction of a physical host machine,
 Hypervisor intercepts and emulates instructions from VMs, and
allows management of VMs,
App
App
 Provide infrastructure API:
 Plug-ins to hardware/support structures
OS
OS
App
OS
Hypervisor
Hardware
Virtualized Stack
Virtual Machines
 VM technology allows multiple virtual machines to
run on a single physical machine.
App
App
App
App
App
Guest OS
(Linux)
Guest OS
(NetBSD)
Guest OS
(Windows)
VM
VM
VM
Virtual Machine Monitor (VMM) / Hypervisor
Hardware
Xen
VMWare
UML
Denali
etc.
Performance: Para-virtualization (e.g. Xen) is very close to raw physical performance!
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What is the purpose and benefits?
 Cloud computing enables companies and applications,
which are system infrastructure dependent, to be
infrastructure-less.
 By using the Cloud infrastructure on “pay as used and on
demand”, all of us can save in capital and operational
investment!
 Clients can:
 Put their data on the platform instead of on their own desktop
PCs and/or on their own servers.
 They can put their applications on the cloud and use the servers
within the cloud to do processing and data manipulations etc.
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Cloud-Sourcing
 Why is it becoming a Big Deal:
 Using high-scale/low-cost providers,
 Any time/place access via web browser,
 Rapid scalability; incremental cost and load sharing,
 Can forget need to focus on local IT.
 Concerns:
 Performance, reliability, and SLAs,
 Control of data, and service parameters,
 Application features and choices,
 Interaction between Cloud providers,
 No standard API – mix of SOAP and REST!
 Privacy, security, compliance, trust…
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Some Commercial Cloud Offerings
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Cloud Taxonomy
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Cloud Storage
 Several large Web companies are now
exploiting the fact that they have data storage
capacity that can be hired out to others.
 allows data stored remotely to be temporarily cached
on desktop computers, mobile phones or other
Internet-linked devices.
 Amazon’s Elastic Compute Cloud (EC2) and
Simple Storage Solution (S3) are well known
examples
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Amazon Simple Storage Service (S3)
 Unlimited Storage.
 Pay for what you use:
$0.20 per GByte of data transferred,
$0.15 per GByte-Month for storage used,
Second Life Update:
1TBytes, 40,000 downloads in 24 hours - $200,
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Utility Computing – EC2
 Amazon Elastic Compute Cloud (EC2):
 Elastic, marshal 1 to 100+ PCs via WS,
 Machine Specs…,
 Fairly cheap!
 Powered by Xen – a Virtual Machine:
 Different from Vmware and VPC as uses “para-virtualization”
where the guest OS is modified to use special hyper-calls:
 Supports “Live Migration” of a virtual machine between hosts.
 Linux, Windows, OpenSolaris
 Management Console/AP
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EC2 – The Basics
 Load your image onto S3 and register it.
 Boot your image from the Web Service.
 Open up required ports for your image.
 Connect to your image through SSH.
 Execute you application…
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Opportunities and Challenges
 The use of the cloud provides a number of
opportunities:
 It enables services to be used without any
understanding of their infrastructure.
 Cloud computing works using economies of scale:
It potentially lowers the outlay expense for start up companies,
as they would no longer need to buy their own software or
servers.
Cost would be by on-demand pricing.
Vendors and Service providers claim costs by establishing an
ongoing revenue stream.
 Data and services are stored remotely but accessible
from “anywhere”.
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Opportunities and Challenges
 In parallel there has been backlash against cloud
computing:
 Use of cloud computing means dependence on others and that
could possibly limit flexibility and innovation:
 The others are likely become the bigger Internet companies like
Google and IBM, who may monopolise the market.
 Some argue that this use of supercomputers is a return to the time
of mainframe computing that the PC was a reaction against.
 Security could prove to be a big issue:
 It is still unclear how safe out-sourced data is and when using these
services ownership of data is not always clear.
 There are also issues relating to policy and access:
 If your data is stored abroad whose policy do you adhere to?
 What happens if the remote server goes down?
 How will you then access files?
 There have been cases of users being locked out of accounts and
69 data.
losing access to
Advantages of Cloud Computing
 Lower computer costs:
 You do not need a high-powered and high-priced computer to run
cloud computing web-based applications.
 Since applications run in the cloud, not on the desktop PC, your
desktop PC does not need the processing power or hard disk
space demanded by traditional desktop software.
 When you are using web-based applications, your PC can be less
expensive, with a smaller hard disk, less memory, more efficient
processor...
 In fact, your PC in this scenario does not even need a CD or DVD
drive, as no software programs have to be loaded and no
document files need to be saved.
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Advantages of Cloud Computing
 Improved performance:
 With few large programs hogging your computer's memory, you
will see better performance from your PC.
 Computers in a cloud computing system boot and run faster
because they have fewer programs and processes loaded into
memory…
 Reduced software costs:
 Instead of purchasing expensive software applications, you can
get most of what you need for free-ish!
 most cloud computing applications today, such as the Google Docs suite.
 better than paying for similar commercial software
 which alone may be justification for switching to cloud applications.
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Advantages of Cloud Computing
 Instant software updates:
 Another advantage to cloud computing is that you are no longer faced
with choosing between obsolete software and high upgrade costs.
 When the application is web-based, updates happen automatically
 available the next time you log into the cloud.
 When you access a web-based application, you get the latest version
 without needing to pay for or download an upgrade.
 Improved document format compatibility.
 You do not have to worry about the documents you create on your
machine being compatible with other users' applications or OSes
 There are potentially no format incompatibilities when everyone is
sharing documents and applications in the cloud.
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Advantages of Cloud Computing
 Unlimited storage capacity:
 Cloud computing offers virtually limitless storage.
 Your computer's current 1 Tbyte hard drive is small compared to
the hundreds of Pbytes available in the cloud.
 Increased data reliability:
 Unlike desktop computing, in which if a hard disk crashes and
destroy all your valuable data, a computer crashing in the cloud
should not affect the storage of your data.
 if your personal computer crashes, all your data is still out there in
the cloud, still accessible
 In a world where few individual desktop PC users back up their
data on a regular basis, cloud computing is a data-safe
computing platform!
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Advantages of Cloud Computing
 Universal document access:
 That is not a problem with cloud computing, because you do not
take your documents with you.
 Instead, they stay in the cloud, and you can access them
whenever you have a computer and an Internet connection
 Documents are instantly available from wherever you are
 Latest version availability:
 When you edit a document at home, that edited version is what
you see when you access the document at work.
 The cloud always hosts the latest version of your documents
 as long as you are connected, you are not in danger of having an outdated
version
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Advantages of Cloud Computing
 Easier group collaboration:
 Sharing documents leads directly to better collaboration.
 Many users do this as it is an important advantages of cloud
computing
 multiple users can collaborate easily on documents and projects
 Device independence.
 Changes to computers, applications and documents follow you
through the cloud.
 Move to a portable device, and your applications and documents
are still available.
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Disadvantages of Cloud Computing
 Requires a constant Internet connection:
 Cloud computing is impossible if you cannot connect
to the Internet.
 Since you use the Internet to connect to both your
applications and documents, if you do not have an
Internet connection you cannot access anything, even
your own documents.
 A dead Internet connection means no work and in
areas where Internet connections are few or
inherently unreliable, this could be a deal-breaker.
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Disadvantages of Cloud Computing
 Does not work well with low-speed connections:
 Similarly, a low-speed Internet connection, such as that found
with dial-up services, makes cloud computing painful at best and
often impossible.
 Web-based applications require a lot of bandwidth to download,
as do large documents.
 Features might be limited:
 This situation is bound to change, but today many web-based
applications simply are not as full-featured as their desktopbased applications.
 For example, you can do a lot more with Microsoft PowerPoint than
with Google Presentation's web-based offering
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Disadvantages of Cloud Computing
 Can be slow:
 Even with a fast connection, web-based applications
can sometimes be slower than accessing a similar
software program on your desktop PC.
 Everything about the program, from the interface to
the current document, has to be sent back and forth
from your computer to the computers in the cloud.
 If the cloud servers happen to be backed up at that
moment, or if the Internet is having a slow day, you
would not get the instantaneous access you might
expect from desktop applications.
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Disadvantages of Cloud Computing
 Stored data might not be secure:
 With cloud computing, all your data is stored on the
cloud.
The questions is How secure is the cloud?
 Can unauthorised users gain access to your confidential
data?
 Stored data can be lost:
 Theoretically, data stored in the cloud is safe, replicated
across multiple machines.
 But on the off chance that your data goes missing, you
have no physical or local backup.
Put simply, relying on the cloud puts you at risk if the cloud lets
you down.
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Disadvantages of Cloud Computing
 HPC Systems:
 Not clear that you can run compute-intensive HPC applications
 Scheduling is important with this type of application
 as you want all the VM to be co-located to minimize communication
latency!
 General Concerns:
 Each cloud systems uses different protocols and different APIs
 may not be possible to run applications between cloud based systems
 Amazon has created its own DB system (not SQL 92), and workflow
system (many popular workflow systems out there)
 so your normal applications will have to be adapted to execute on these
platforms.
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Advantages and Disadvantages: Summary
 Advantages











 Disadvantages
Lower computer cost

Improved performance

Reduced software cost
Instant software update

Improved doc. Format

compatibility
Unlimited capacity
Increased data reliability
Universal doc. Access
Version control and availability
Easy group collaboration
Portability, device independence
Requires const. internet
connection
Bad performance with low
speed connection
Limited features
Security and data loss
issues
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Types of Cloud
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Public Cloud
 A public cloud is one in which the services and infrastructure are
provided off-site over the Internet. These clouds offer the greatest
level of efficiency in shared resources; however, they are also more
vulnerable than private clouds. A public cloud is the obvious choice
when
 Your standardized workload for applications is used by lots of
people, such as e-mail.
 You need to test and develop application code.
 You have SaaS (Software as a Service) applications from a vendor
who has a well-implemented security strategy.
 You need incremental capacity (the ability to add computer capacity
for peak times).
 You’re doing collaboration projects.
 You’re doing an ad-hoc software development project using a
Platform as a Service (PaaS) offering cloud.
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Private Cloud
 A private cloud is one in which the services and infrastructure are
maintained on a private network. These clouds offer the greatest
level of security and control, but they require the company to still
purchase and maintain all the software and infrastructure, which
reduces the cost savings. A private cloud is the obvious choice
when
 Your business is your data and your applications. Therefore, control
and security are paramount.
 Your business is part of an industry that must conform to strict
security and data privacy issues.
 Your company is large enough to run a next generation cloud data
center efficiently and effectively on its own.
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Hybrid Cloud
 A hybrid cloud includes a variety of public and private options with
multiple providers. By spreading things out over a hybrid cloud, you
keep each aspect at your business in the most efficient environment
possible. The downside is that you have to keep track of multiple
different security platforms and ensure that all aspects of your
business can communicate with each other. Here are a couple of
situations where a hybrid environment is best.
 Your company wants to use a SaaS application but is concerned
about security. Your SaaS vendor can create a private cloud just for
your company inside their firewall. They provide you with a virtual
private network (VPN) for additional security.
 Your company offers services that are tailored for different vertical
markets. You can use a public cloud to interact with the clients but
keep their data secured within a private cloud.
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Cloud Categories
 Many IT department executives are concerned about public cloud
security and reliability. Take extra time to ensure that you have
security and governance issues well planned, or the short-term cost
savings could turn into a long-term nightmare.
 To complicate things, the lines between private and public clouds
are blurring. For example, some public cloud companies are now
offering private versions of their public clouds. Some companies that
only offered private cloud technologies are now offering public
versions of those same capabilities.
 The management requirements of cloud computing become much
more complex when you need to manage private, public, and
traditional data centers all together. You'll need to add capabilities
for federating these environments.
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