charm(a cost-efficient multi-cloud data hosting scheme with high availability)

IntroductionMulti-Cloud Scenario

MotivationAvailable Data Hosting SchemesThe proposed Scheme CHARMConclusion and Future Scope

CHARM(A Cost-Efficient Multi-Cloud Data Hosting

Scheme with High Availability)

Deeksha [email protected]

Computer Engineering DepartmentNIT Kurukshetra

May 5, 2016

Deeksha Arya CHARM: Multi-Cloud Data Hosting Scheme

[email protected]



Outline1 Introduction

Cloud Computing2 Multi-Cloud Scenario

Single Cloud vs Multi-CloudProblems in Single Cloud Data HostingProblems in Multi-Cloud Data Hosting

3 Motivation4 Available Data Hosting Schemes

ReplicationErasure Coding

5 The proposed Scheme CHARMArchitectureAlgorithms Used

6 Conclusion and Future ScopeDeeksha Arya CHARM: Multi-Cloud Data Hosting Scheme



Cloud Computing

What is Cloud Computing?

Cloud Computing is the use of computing resources(hardwareand software) that are delivered as a service over a network.




Cloud Computing

How does it work?

In cloud computing, users access the data, applications or anyother services with the help of a browser regardless of the deviceused and the user’s location.




Cloud Computing

Why Cloud Computing?




Cloud Computing

History of Cloud Computing




Cloud Computing

Different Cloud Vendors




Single Cloud vs Multi-CloudProblems in Single Cloud Data HostingBasic Principle of Multi-cloud Data HostingProblems in Multi-Cloud Data Hosting

Single Cloud vs Multi Cloud

Which one is more beneficial?

How to decide?

Who will decide?

What if the situation changes?





Heterogeneous Clouds

Existing clouds exhibit great heterogeneities in terms of bothworking performances and pricing policies.

For instance,

Google Cloud Storage charges more for bandwidthconsumption,Amazon S3 charges more for storage space





Vendor Lock-in Risk

Customers usually put their data into a single cloud and thensimply trust to luck. This is subject to the so-called vendorlock-in risk, because customers would be confronted with adilemma if they want to switch to other cloud vendors.

For example, moving 100 TB of data from AmazonS3(California data-center)to Aliyun OSS (Beijing data-center)would consume as much as 12,300 (US) dollars.





The vendor lock-in risk makes customers suffer from priceadjustments of cloud vendors.

Another issue is availability.

Clearly, it is unwise for an enterprise or an organization tohost all data in a single cloud— “your best bet is probably notto put all your eggs in one basket ”.





Multi-Cloud Scenario

Basic Principle of Multi-cloud Data Hosting





Problems in Multi-Cloud Data Hosting

Two critical problems:

1 How to choose appropriate clouds to minimize monetary costin the presence of heterogeneous pricing policies?

2 How to meet the different availability requirements of differentservices?




Motivation

Major concern for customers: Which cloud(s) are suitablefor storing their data and what hosting strategy ischeaper?

CHARM-the proposed Data Hosting scheme helps thecustomers to select several suitable clouds and an appropriateredundancy strategy to store the data with

1. Minimum monetary cost and2. Guaranteed Availability

In addition, it also provides the function of re-distributingthe data according to the variations of data access patternsand pricing of clouds.





Available Data Hosting Schemes

Available Redundancy Mechanisms for Data Hosting:

1. Replication2. Erasure Coding

Different schemes uses these redundancy mechanisms indifferent ways( Random/Greedy).





Replication

Traditional Storage Mode: Put the replicas into threedifferent storage nodes.

Advantages:

Provides High AvailabilityThe data is lost only when the three nodes all crash.

Dis-advantage: Occupies 2x more storage space.





Erasure Coding

Erasure coding is proposed to reduce storage consumptiongreatly while guaranteeing the same or higher level of datareliability as that of Replication.

Reed-Solomon code - A representative erasure-coding scheme:

Data of a segment is encoded into n blocks including

1. m data blocks and,2. n-m coding blocks

These blocks are put into n different clouds.Data can be restored using any m chunks in the segment.





Erasure Coding

Advantages:

Data availability can be guaranteed with lower storage space(compared with replication).Up to n −m simultaneous chunk failures can be tolerated.

Dis-advantages:

A read access has to be served by multiple clouds that storethe corresponding data blocks.Consequently, erasure coding cannot make full use of thecheapest cloud as what replication does.





Replication in terms of Erasure Coding

Replication is a special case of Erasure Coding with m=1.

That is, in Replication we have

m = 1 data blockn −m = n − 1 coding blocks andUp to n −m = n − 1 simultaneous failures can be tolerated.




ArchitectureAlgorithms Used

CHARM

CHARM stands for a Cost-efficient data Hosting model withhigh Availability in heteRogenous Multi-cloud system.

CHARM combines the two widely used redundancymechanisms, i.e., replication and erasure coding.

CHARM ≡ (Replication + Erasure Coding)





Architecture of CHARM





Multi-Cloud Scenario

Basic Principle of Multi-cloud Data Hosting





Components of CHARM

There are four main components in CHARM:

1. Data Hosting

2. Storage Mode Switching (SMS)

3. Workload Statistic

4. Predictor





Working of the Components

1. Data Hosting stores data using replication or erasure coding,according to the size and access frequency of the data.

2. Storage Mode Switching (SMS) decides whether thestorage mode of certain data should be changed fromreplication to erasure coding or in reverse, according to theoutput of Predictor.

3. Workload Statistic keeps collecting and tackling access logsto guide the placement of data. It also sends statisticinformation to Predictor which guides the action of SMS.

4. Predictor is used to predict the future access frequency offiles.





Algorithm 1





Key Points

1. What should be the value of n? (n varies from 2 to nmax )

2. Which n clouds should be selected?

3. What should be the value of m? (m varies from 1 to n )

4. Goals:

Minimize the costMaximize the availability

5. Complexity of the Algorithm: O(NLogN)





Algorithm 2




Conclusion and Future Scope

CHARM makes fine-grained decisions about which storagemode to use and which clouds to place data in and hencehelps the user to distribute the data on different clouds in acost effective manner.

This system can be enhanced by developing an automaticupdate methodology that updates only the required datablocks.

The enhanced version will save the time for downloading anduploading the file again.




References

Quanlu Zhang, Shenglong Li, Zhenhua Li, Yuanjian Xing, Zhi Yang, andYafei Dai (2015)

CHARM: A Cost-Efficient Multi-Cloud Data Hosting Scheme with HighAvailability

IEEE TRANSACTIONS ON CLOUD COMPUTING, VOL. 3, NO. 3,372-386, JULY-SEPTEMBER 2015.

Gade Pooja V., Mate Shweta, A. Janjalkar Priti S. (2015)

Multi-Cloud Hosting for Performance Optimization and Security

International Journal for Scientific Research and Development, VOL. 3,Issue 8 — ISSN (online), 2321-0613 2015.




Thank You!
