consistency as a service: trading consistency for availability

8/17/2019 Consistency As A Service: Trading Consistency for Availability

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Consistency As A Service: Trading Consistency for Availability

Pratik S. Mahajan

Department of CSE, Government College of Engineering, Aurangabad, India

Email: csepratikmahajangmail!com

Shubhangi Sapkal

Department of "CA, Government College of Engineering, Aurangabad, India

Dr. . . Desh!ukh

Department of CSE and I#, Dr! $A"%, Aurangabad, India

Abstract & As more and more charities and libraries move to

cloud services, this technolog' is no longer novel( it)s becoming the dominant paradigm in I#! A cloud storage facilit'is a need of an hour as it facilitates elasticit'&so resourceallocation can get bigger or smaller depending on a users*demand, Elasticit' enables scalabilit'&so that the cloud canscale up +hen demand is high and do+n for less demand e!g!

allo+s for scale +hen an application in the cloud adds users,etc!-, .esource /ooling, 0n Demand, Self1Service /rovisioningi!e client can re2uest desire service from cloud vendor and3456 service i!e high availabilit' at cheapest price !$ut the ke'hindrance come +hen +e need high availabilit'(as it needed tocreate plent' of copies of single file and at different

geograph' !#o attain high consistenc' more mone' is needed!In this paper, +e have presented uni2ue, innovative, efficientand effective consistenc' as a service CaaS- model, +hichconsists of a various large capacit' data clouds and small auditclouds !Data clouds are used to store clients actual data offered b' Cloud vendors like Google, Ama7on, "icrosoft, etc !and

Audit cloud are used to check consistenc' of cloud ismaintained accuratel' or not! At the last +e have appliedtraditional approach to audit purpose i!e 8euristic AuditingStrateg' +hich uses 3 algorithm vi7 9ocal and Global AuditingStrateg'! 9oosel' s'nchroni7ed clock is needed to audit purpose! 8euristic Auditing Strateg' is used to find violations

in consistenc' terms i!e! document is modified or safe!

e'+ords & Audit Cloud, Consistenc' as a service CaaS-,

Data Cloud, Global Auditing, 9ocal Auditing!

I! I;#.0D%C#I0;

Cloud Computing is still a bu77+ord or uncleared to man' people!#he definition mostl' used toda' is the one e? meanseither +e can provide availabilit' or consistenc' #here are man' differences in Cloud Computing andtraditional transactional databases related to consistenc'

re2uirement! As in cloud, there is data duplication is taken place i!e! data is geographicall' distributed to get higher

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https://en.wikipedia.org/wiki/Disk_imagehttps://en.wikipedia.org/wiki/Disk_imagehttps://en.wikipedia.org/wiki/Block_storagehttps://en.wikipedia.org/wiki/Object_storagehttps://en.wikipedia.org/wiki/VLANhttps://en.wikipedia.org/wiki/VLANhttps://en.wikipedia.org/wiki/Disk_imagehttps://en.wikipedia.org/wiki/Disk_imagehttps://en.wikipedia.org/wiki/Block_storagehttps://en.wikipedia.org/wiki/Object_storagehttps://en.wikipedia.org/wiki/VLANhttps://en.wikipedia.org/wiki/VLAN


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degree of performance! $ut duplicated file needs strongconsistenc' to keep the consistenc' bet+een a file and itsreplicas and simultaneousl' the overhead of consistenc'

maintenance is determined b' the number of replicas!Connecting these t+o components +ill increase the s'stem performance! Consistenc' is ensured b' s'nchroni7ation

bet+een the copies! Consider the scenario in Fig!@, +here .aj and Simran+orking on single project together using cloud facilit' +here

data is replicated to distributed data servers CS@, CS3, CS,CS4,and CS! After uploading a ne+ version of there2uirement anal'sis to a CS 4,Simran calls .aj to do+nload

the latest version for integrated design! 8ere, after Simran calls.aj, the causal relationship ? is established bet+een

Simran*s

update and .aj*s read! #herefore, the cloud should providecausal consistenc', +hich ensures that Simran*s update iscommitted to all of the replicas before .aj*s read! If the cloud provides onl' eventual consistenc', then .aj is allo+ed toaccess an old version of the re2uirement anal'sis from CS!If

the old version is used,it ma' not satisf' the customer*sactual re2uirement!

As per the Cloud Computing feature data should availableal+a's to the client +hich are replicated at multiplegeographical locations! #he main problem +ith consistenc'feature of cloud( it costs ver' high to attain strong consistenc'means updated cop' present al+a's to the client! So most of

the cloud vendors provide +eak consistenc' like eventualconsistenc', +here client sees slightl' old data! Eventualconsistenc' provides ver' high reliabilit' and high performance +hich is the re2uirement of domain name s'stem!%pdates to a name +ill not be visible immediatel', but allclients are ensured to see them eventuall'!

8o+ever, eventual

consistenc' is not a catholicon for all applications! Especiall'for the interactive applications, stronger consistenc' assuranceis of increasing importance! $ut different applications re2uireddifferent consistencies like mail services need monotonic readconsistenc' and read 'our +rite consistenc' +hile socialnet+ork need causal consistenc'!

!

Fig.1: An application that requires causal consistency.

.

II! .E9A#ED H0.

A cloud is essentiall' a large1scale distributed s'stem

+here each piece of data is replicated on multiplegeographicall'1 distributed servers to achieve highavailabilit' and high performance! #hus, +e first revie+the consistenc' models in distributed s'stems! As a

standard te


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Concurrent +rites ma' be seen in a different order on differentmachines!

Client centric consistenc' models Concerns consistenc'e


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All other users +ill send their %0#s to the auditor for

obtaining a global trace of operations! After e


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Fig. & Auditing 'eport

B! C0;C9%SI0;

Consistenc' as a service CaaS- model and a t+o1level auditingstructure to help users validate +hether the cloud service provider CS/- is providing the promised consistenc' and to2uantif' the severit' of the violations is an' !Hith the CaaSmodel, the users can assess the 2ualit' of cloud services andselect a right cloud service provider among various candidates ,

for e in /roc! 3OO6 AC" S0S/!?6Rin 9iu, Guojun Hang ,>Consistenc' As A Service:Auditing Cloud>, IEEE #ransactions 0n ;et+ork And

Service "anagement, Bol! @@, ;o! @, "arch 3O@4!

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consistency as a service: trading consistency for availability

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