COMMUNITY CLOUD

Cloud Computing for the Community

Marte K. Skadsem

Northern Research Institute, P.O. Box 6434, TromsøScience Park, N-9294 Tromsø, Norway

Randi Karlsen

Dep. of Computer Science, University of Tromsø, N-9294 Tromsø, Norway

Gordon Blair, Keith Mitchell

School of Computing and Communications, InfoLab21, Lancaster University, Lancaster, LA1 4WA, U.K.

Keywords:

Cloud computing, Community cloud.

Abstract:

Commercial clouds have gained a lot of popularity because of easy access to high quality services. Private

clouds and community clouds have emerged as an answer to the security concerns raised by commercial

clouds. A community cloud is build up by resources made available by the community members and provides

services adapted to the needs of the community. In this paper we present a community cloud design that focus

on the properties of the social bindings within a community and look at how the characteristics of a community

can effect the cloud.

1 INTRODUCTION

Clouds and Cloud Computing have gained a lot of

popularity among enterprises due to their easy use,

low administration costs, and an illusion of access

to endless amounts of resources. But moving data

and computations to commercial cloud services raises

many questions around location and ownership of

your personal data. Where is your data stored? Who

owns your data when it is not stored on your own

computer? What happens if the vendor you buy or use

services from closes down? Will you have a chance

to get your data back? Will it be sold to other cloud

providers?

In this paper we are proposing a community cloud

design that aims to alleviate some of these concerns.

In a community cloud environment, small communi-

ties share their existing resources to form a cloud that

provide services for user generated data. We deﬁne a

community as a group of people connected together

through a common interest, like a village, family or

interest group. Resources that a community cloud ser-

vice is able to offer include storage, processing power

and application sharing.

Within a community cloud scenario, the cloud itself

is owned, operated and controlled by the community

themselves who may be regarded as a type of social

network, and the properties of the social relationships

within the network can be utilized in the cloud design

and operation. To achieve this a community cloud

design is open for its members and a low barrier to

entry must be adopted.

The outline of this paper is as follows: In section

2 related work is presented. Our approach to a com-

munity cloud is presented in section 3. Section 4 de-

scribes the architecture and design of the community

cloud, and the paper is concluded in section 5.

2 RELATED WORK

The main motivations for moving computation to the

cloud are cost and the promise of easily accessible,

almost endless amount of resources. Users of cloud

computing do not need to buy, administrate and main-

tain large data centers, clusters or grids themselves as

this is provided by the cloud. Most cloud providers

offer their services on a pay-per-use model in which

418

K. Skadsem M., Karlsen R., Blair G. and Mitchell K..

COMMUNITY CLOUD - Cloud Computing for the Community.

DOI: 10.5220/0003389404180423

In Proceedings of the 1st International Conference on Cloud Computing and Services Science (CLOSER-2011), pages 418-423

ISBN: 978-989-8425-52-2

 2011 SCITEPRESS (Science and Technology Publications, Lda.)

you only pay for the resources you use at any given

time. This gives good elasticity as clouds will au-

tomatically expand when more resources are needed

and contract when the demand is lower. A good

overview of cloud computing can be found in (Arm-

brust et al., 2009).

Moving data and computation to the cloud is con-

venient, however, this convenience comes at the cost

of control. Control over the network, implementa-

tion, interfaces etc. stays with the cloud provider

and the customer is bound to the terms of services

with the provider. Many are pointing out the danger

of data lock-in in clouds, among them the founder

of the Free Software foundation, Richard Stallmann

(Johnson, 2008). Since, in general, most of the APIs

for cloud computing services are proprietary, moving

from one cloud service provider to another is not triv-

ial (Armbrust et al., 2009) and getting data out is not

easy, if possible at all. This prevents many potential

customers from moving to the cloud. Another prob-

lem with the clouds is that they are public and do not

offer any security for ensuring privacy (Wood et al.,

2009). For enterprises it is crucial to know that their

data is not easily attacked or leaked to third parties.

Because of the security concerns, private clouds,

sometimes called internal clouds, have emerged as

clouds behind a ﬁrewall that are not globally acces-

sible. Private clouds are by some not recognized as

“real clouds” as it is not possible for the enterprise

who owns the private cloud to outsource the heavy

computation and maintenance of a large data cen-

ter. Hence private clouds may not offer as good and

elastic services as a commercial cloud. The Cloud-

Net project (Wood et al., 2009) is one attempt to

merge private clouds with commercial vendor pro-

vided clouds by utilizing Virtual Private Networks.

In (Marinos and Briscoe, 2009) a community

cloud is presented as a virtual data center made up of

available resources of networked personal computers

which are self conﬁgurable and adaptable. The basic

architecture comprises of three layers where the core

infrastructure is a Peer-to-Peer (P2P) network of vir-

tual machines. As the nodes participate both as con-

tributors and consumers, a “community currency” is

needed that ensures that a node has to contribute in

order to consume (Marinos and Briscoe, 2009). The

application areas the authors envision are community

hosted versions of Wikipedia and YouTube.

From a user’s point of view the community cloud

does not look any different from an ordinary cloud.

The distribution and underlying organization of the

cloud is not visible outside the cloud. The user will

have to know about the community currency and that

contribution of resources to the cloud is necessary for

consumption, but except for that the community cloud

looks just like any other cloud.

The authors of (Marinos and Briscoe, 2009) are

concerned about the control that cloud computing

providers have and this is the main motivation for

proposing the community cloud computing approach.

While we share the same security and privacy con-

cerns we are also interested in supporting cloud based

services within communities that are poorly con-

nected to the Internet. In many European countries

there are a signiﬁcant proportion of the population

whom do not have high-speed access to the Internet,

especially in rural communities. In the U.K, for ex-

ample, the term ’ﬁnal third’ has recently been coined

and relates to the fact the almost 30 percent of the

population are unable to achieve speeds of 2Mbps.

Therefore, our approach to the community cloud dif-

fers in that we want a more open version of the cloud

with more focus on the properties of the community

and inclusion of the community.

3 COMMUNITY CLOUD

3.1 Community Clouds vs Commercial

Clouds

We use the term “community cloud” to describe pri-

vate clouds adapted for smaller environments like a

local community, a school or a home. The difference

between the commercial vendor clouds and commu-

nity clouds are shown in ﬁgure 1 and ﬁgure 2. In a

commercial cloud users connect to the cloud, put data

in it and get data and/or results back. The users do

not take part in the cloud in any other way, and do not

know anything about how the cloud is constructed or

where it actually is located (ﬁgure 1). In the commu-

nity cloud a group of users connects their computers

to form the basic cloud infrastructure. The users con-

nect and use the community cloud much in the same

way as they do with a commercial cloud, but the cloud

infrastructure is open and controlled by the participat-

ing users (ﬁgure 2).

In a community cloud each member of the com-

munity contribute with resources to the cloud infras-

tructure, forming a Peer-to-Peer (P2P) network. In-

formation about the type and amount of available re-

sources is open and known to all participants at all

time. The community cloud will provide services for

user generated data based on the needs of the com-

munity. Because the infrastructure is open it is eas-

ily controlled by the community, and the commu-

nity cloud will be adaptable to offer new services as

COMMUNITY CLOUD - Cloud Computing for the Community

419

Figure 1: The commercial cloud. The users put data to the

cloud and get data and/or results back.

needed. The social relationships within a community

will set the premises for the community cloud proper-

ties. We will look more at this in section 3.3

3.2 Illustrative Applications

Before we go into a more detailed description we

would like to give two examples of how a community

cloud may be used.

3.2.1 Editing Video in Low Resolutions

Consider the situation where a group of people are

making a ﬁlm together. After shooting the ﬁlm they

have lots of raw material to work on. All this raw ma-

terial could be terabytes in size, so editing it requires

lots of processing power and storage.

The members of the group do not live in the same

town. They have normal workstations, and their Inter-

net connections vary in speed and quality. The cutting

and editing of the ﬁlm is a collaboration project, so

each of the group members must be able to download

and edit the ﬁlm as a whole or in parts. In order to do

this efﬁciently, they form a community cloud.

The raw material is distributed and stored among

the group members’ computers by adding it to the

community cloud. Then it is transcoded to a ﬁle for-

mat with lower resolution. The group members will

then work on this smaller ﬁle to edit and ﬁnish the

ﬁlm. At some point, for instance when the whole

ﬁlm is ﬁnished in the low resolution ﬁle format, the

changes are propagated to the raw ﬁlm.

In this example the community cloud will offer

storage and processing services. The ﬁlm is replicated

and stored on the computers of the different group

members. The processing tasks, i.e., the transcoding

and editing, is done on the computers that are best

suited. A computer with a slow CPU will for instance

not be assigned heavy processing. The community

cloud will take care of the distribution of replicated

data and processing tasks, and it will make sure all

Figure 2: Members of a community connect their comput-

ers to form a cloud.

group members are offered the same services despite

different quality in network connections.

3.2.2 Online Message Board for a Village

A small village wants to share an online message

board where local activities can be announced. They

also want a photo sharing service for photos from

these activities and the daily life in the village. The

village has a slow connection to the Internet, and

not all villagers have proper Internet access in their

homes. Because of this, existing services on the In-

ternet cannot be used, so the villagers set up a local

network in which they all contribute to form a com-

munity cloud.

There are a few people in the village who com-

mit themselves to never turn off their computers so it

is possible to always access the data in the cloud. In

addition the local school dedicates one of their com-

puters to the cloud. The rest of the villagers will con-

tribute with resources when their computers are on-

line the local network.

Because of the committed computers the commu-

nity cloud is always accessible. All data in the cloud

will be stored on these computers. Data is also repli-

cated on the computers that are not always connected.

When users connect to the community cloud from

their computers, the computers will become part of

the cloud thus making the cloud able to offer better

accessibility of the replicated data. When more users

connect, the accessibility to the community cloud is

not reduced since every connected user contribute

with more resources and replicas.

While the villagers wants to contribute with re-

sources for the cloud, they are concerned about abuse

and protection of their private data. The community

cloud will have to run isolated on each participating

node and there must exist controlling systems for han-

dling abuse of the cloud.

In this example the community cloud will offer a

local network with storage services. The community

cloud will also offer application services like photo

CLOSER 2011 - International Conference on Cloud Computing and Services Science

420

sharing and a message board. The services will be

available from all computers in the village that are

connected to the local network even if they do not

have an Internet connection.

3.3 Communities

As we can see from the examples above, quite differ-

ent communities can make use of a community cloud

environment and we will now take a closer look at the

properties of the communities.

As mentioned in the introduction, we deﬁne a

community as a group of people that are connected

through a common interest. This implies that a com-

munity cloud can consist of heterogeneous resources

that are geographically spread and have a variable

network connection between them. It also implies that

the people forming a community to a certain degree

know and trust each other.

The community is a social network where all the

users participate with whatever resources they have

available. The underlying distribution and hetero-

geneity among resources are visible for the users. The

users will have access to a larger amount of resources

than what they have with only their own computer,

like in commercial clouds, but at the same time they

know the resources are available with the properties

and limits of the community.

When the community is your social network, or

parts of your social network, the trust and nature of

the relationships between the members will make the

community currency used in (Marinos and Briscoe,

2009) redundant. The members trust that everyone

participate with as much resources as they can be-

cause they all have a common goal, or interest, in

making the community cloud as good as possible.

Participating in a community cloud puts expectations

and obligations on the users. If a user consumes a lot

of resources but provides little to the community, the

other users will cut the “free rider” off the commu-

nity cloud. Hence everyone should feel obligated to

participate and will act to the best of the community.

3.4 Properties and Challenges

We will now look at the properties and challenges

for the community cloud based on the requirements

from the application examples and the properties of

the communities.

Services the community cloud will offer are stor-

age, processing and applications, depending of the

needs of the community. The community cloud will

hence offer Software as a Service (SaaS) to the users,

but it will also offer Infrastructure as a Service (IaaS)

for those wanting to implement and adapt their own

services.

The community cloud must be made from the het-

erogeneous resources that the community already has

available. Also, the community cloud architecture

must be able to handle varying network speed be-

tween the participating machines and also that ma-

chines will become unavailable for periods of time

because users turn them off.

As we have seen, communities differ greatly in

“personality”. Although the services used by differ-

ent communities are the same, the communities will

differ in available resources and so the services will

have to be adaptable for this. Building this kind of

infrastructure is challenging.

The key for solving these challenges lies in the

opportunity given by the social relationships and the

natural trust within a community. Different commu-

nities will have different levels of trust. An open in-

frastructure where knowledge about the environment

is available for all participants at all time is strength-

ening the trust. The trust is also strengthened by the

common interest, or the common goal, shared in the

community.

An important property for the community cloud

will therefore be openness and common knowledge of

the environment that is accessible at any time for all

participants. This knowledge include what kind of re-

sources that exist in the community cloud, how much

is currently available, but also statistics of each user’s

usage of the cloud. The usage statistics will help de-

tect if there are any “free riders” using the community

cloud.

4 ARCHITECTURE AND DESIGN

4.1 Community Cloud Design

Figure 3 shows the overall design of the community

cloud architecture. At the bottom of the ﬁgure we ﬁnd

the existing resources of the community. Depending

on the community this can be everything from ordi-

nary workstations, to PlayStation. How much and

what kind of resources, i.e. how much storage and

processing power, these can offer to the community

cloud are reported to a community resource manager.

The community resource manager will coordinate the

available resources to operate as a cloud. Services

can be built on top of the community cloud based on

the resource information available through the com-

munity resource manager’s service interface. Users

will then be able to use the services their community

cloud offer.

COMMUNITY CLOUD - Cloud Computing for the Community

421

Figure 3: The community cloud design. The existing resources reports their available resources to a community resource

manager that coordinates the available resources and offer an interface which services can use.

Grid and P2P networks are possible alternatives for

the community cloud design. Because of the dynamic

and heterogeneous environment a community repre-

sents we will base the cloud on a P2P architecture.

4.2 The Community Resource Manager

The community resource manager keeps control over

cloud participants, available resources and the prop-

erties of these resources. It also keeps an overview

of the applications the cloud offers to its users, and it

knows the current status of the whole cloud. Based

on this information the community resource manager

is able to map the applications’ requested resources to

the available resources.

In order to do this mapping the community cloud

needs to be able to describe requirements and avail-

able resources. I.e. we need to describe applica-

tions, data, storage and processing power. For this

we will use JSON (JavaScript Object Notation), a

lightweight, text-based, language-independent data

interchange format (Crockford, 2006).

A P2P architecture implies a fully distributed

system, however the community resource manager’s

tasks are better handled centralized on a single node.

To make sure the community resource manager does

not represent a single point of failure, we will make

it soft state, similar to the master in Google File Sys-

tem (Ghemawat et al., 2003). This means that any

participating node can be elected as community re-

source manager as it will rebuild the required state

when selected. It also means that the community re-

source manager will not represent a single point of

failure as the cloud will not collapse if the node run-

ning the community resource manager fails.

In order for the community resource manager to

be soft state, its state must be re-produceable by any

participating node. This means that the state is dis-

tributed in the cloud, and that each node knows a part

of the cloud’s current state. The community cloud

will use round robin DNS. When someone contacts

the system, they do not know which speciﬁc node they

are talking to. The node that establish contact with a

user is caching all data and information it gets while

responding to the user’s request. When it gets a re-

quest it cannot handle, it asks the community resource

manager for help.

4.3 Architecture

The community cloud architecture is based on an ex-

isting storage and processing system made of a P2P

based storage network, called DeStore, and its pro-

cessing interface, DeLight.

In DeStore several heterogeneous computers col-

laborate to provide a replicated storage area that can

be exported as a single storage service (Borch and

Heggelund, 2007).

Key features of the storage network are:

• Designed to run on commodity hardware. It is

possible to run DeStore on hardware already ex-

isting in a community.

• Easy to extend the storage capacity on demand.

When more storage is needed, new nodes are just

added to the network. This is possible because

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422

DeStore is a self-organizing P2P network.

• Policy based replication and replication level is re-

cursively conﬁgurable for each directory.

DeStore is composed of two different types of

nodes; slaves and masters. The master performs syn-

chronized jobs within the network. This includes

locking/unlocking operations, caching of authentica-

tion and giving replication jobs to slaves. A slave, the

basic DeStore node, stores and replicates data and can

provide HTTP or WebDAV access to the data. Re-

quested data that is not available locally on a slave

will be fetched from a replica and provided to the

requester. Hence the requester (a WebDAV enabled

client) does not need to be aware of the underlying

distribution.

The community resource manager in the commu-

nity cloud corresponds to DeStore’s master node.

DeLight (Skadsem et al., 2009) extends DeStore

to include processing on the stored data. DeLight

takes advantage of DeStore’s support for heterogene-

ity by building a network of nodes able to either store

data, process data, or both, offering a storage network

with integrated processing.

Key features of an integrated storage and process-

ing network:

• Utilization of each node’s individual properties so

that the nodes are used to what they are good at.

• Data is processed at the same place or close to

where it is stored.This way bandwidth is saved

and latency can be avoided.

• Adaption to individual user demands by offering

applications an interface for adding and running

processing tasks on data stored in DeStore. This

is done by making DeStore able to handle plug-

ins. A plug-in manager running on each node

is responsible for registering and enrolling new

plug-ins in the system. Plug-ins can be added and

removed by user applications during run-time,

and the changes are migrated to all participating

nodes.

The integrated storage and processing system is a

good base to build a community cloud from since it

posses many of properties needed. By extending the

master node it will be able to ﬁll the tasks of the com-

munity resource manager in the community cloud de-

sign. The community resource manager will then do

all the work of the master node, but also keep deﬁ-

nitions on how to describe the community cloud re-

sources and how to represent information about the

infrastructure so that openness and common knowl-

edge about the environment can be achieved.

5 CONCLUSIONS

In this paper we have presented a community cloud

that focus on the properties the social relationships

within a community give to the cloud design. The

community cloud can consist of heterogeneous re-

sources that are geographically spread and have dif-

ferent network connections. The community cloud

offer storage, processing and application services

adapted to the needs of the speciﬁc community. The

cloud design is based on openness to the knowledge

of the environment, meaning that information about

the infrastructure and its resources are available to all

the community members at all time. An integrated

storage and processing network serve as the starting

point for the community cloud architecture.

REFERENCES

Armbrust, M., Fox, A., Grifﬁth, R., Joseph, A. D., Katz,

R., Konwinski, A., Lee, G., Patterson, D., Rabkin, A.,

Stoica, I., and Zaharia, M. (2009). Above the Clouds:

A Berkeley View of Cloud Computing. White paper,

UC Berkeley Reliable Adaptive Distributed Systems

Laboratory.

Borch, N. T. and Heggelund, A. (2007). A read/write dis-

tributed web server. In Proceedings of the Second In-

ternational Conference on Internet Technologies and

Applications (ITA07), Wrexham, Wales.

Crockford, D. (2006). The application/json Media Type for

JavaScript Object Notation (JSON). RFC 4627 (Infor-

mational).

Ghemawat, S., Gobiof, H., and Leung, S.-T. (2003). The

google ﬁle system. In SOSP’03: Proceedings of the

nineteenth ACM Symposium on Operating Systems

Principles, pages 29–43, New York, NY, USA. ACM

Press.

Johnson, B. (2008). Cloud computing is a

trap, warns GNU founder Richard Stallman.

The Guardian, guardian.co.uk. webpage,

http://www.guardian.co.uk/technology/2008/sep/29/c

loud.computing.richard.stallman.

Marinos, A. and Briscoe, G. (2009). Community cloud

computing. In Jaatun, M. G., Zhao, G., and Rong, C.,

editors, Cloud Computing, First International Confer-

ence, CloudCom 2009, Beijing, China, December 1-4,

2009. Proceedings, volume 5931 of Lecture Notes in

Computer Science, pages 472–484. Springer.

Skadsem, M. K., Borch, N., and Karlsen, R. (2009). De-

Light: A Peer-to-Peer storage and processing system.

Internet and Web Applications and Services, Interna-

tional Conference on, 0:97–101.

Wood, T., Shenoy, P., Gerber, A., Ramakrishnan, K. K., and

der Merwe, J. V. (2009). The case for enterprise-ready

virtual private clouds. In Proceedings of the Workshop

on Hot Topics in Cloud Computing (HotCloud’09),

San Diego, CA. USENIX.

COMMUNITY CLOUD - Cloud Computing for the Community

423