Parity Cloud Service

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ANEESH CHANDRAN

ROLL NO 6

S7 R


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Introduction

Parity cloud service (PCS)

Modeling the parity cloud service

Feasibility of the PCS

Conclusions


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The increasing amount of user data provides a

momentum leading to a large capacity storage

device, such as tera -scale HDD

Nowadays, tera-scale HDDs are widely used inPCs

While large capacity storage devices afford

users sufficient space for user data


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A failure of the device causes a great deal of

recovery cost or the loss of the whole user data

users generally equip another storage device

and backup their data External Hard disk and usb drivers are

commonly used external storage devices


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using portable storage devices cannot be a safe

way for personal data backup

A much more safe and reliable way for data

protection is using an expensive system such asRAIDor server as a private backup system

it is not reliable but provide strong privacy

protection


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They are not practical for personal use because

of both the cost and maintenance burden

Recently, lots of internet service providers

(ISPs) provide storage cloud services to theirusers

Provides high reliability, convenience, and low

cost


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There are many users who believe that their

data can be revealed to others

several works pointed out that the privacy

protection is the major problem in cloudcomputing adaptation

encryption-based data protection can solve

the problem

An authorized organization can decrypt theencrypted user data when necessary


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Reliability: The service should be able to

recover user data, when necessary, with

sufficiently high probability

Economical efficiency: The cost for data

recovery service should be sufficiently low to

increase the user accessibility


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Convenience: General users should be able to easily

use the data recovery service.

Privacy protection: User data must not be exposed toanyone other than the owner of the data, neither

intentionally nor unintentionally

Parity Cloud Service (PCS) that satisfies all of the

above criteria


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PCS provides with a parity-based recovery

service

Extremely simple

Can completely relieve users of their concernabout privacy protection

Easy to use

Requires a reasonable server-side cost

Recover user data with sufficiently high

probability


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generates virtual disk in user system for private

data backup

makes parity group across virtual disks of

multiple users stores the parity data of the parity group in the

cloud storage

Each user is enough to backup their files to their

own virtual disk for future data recovery


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If original file is unavailable from the file

system, we can request to the PCS agent

software for the file recovery.


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A PCS agent software, installed in each user

machine

It creates a virtual disk on the user storage

deviceThe Virtual Disk Parity Group (VDPG), whose

parity data are stored in the cloud storage

Parity generation is managed by the PCS server.


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1 .The Virtual Disk Interface : provides

user with interfaces to the virtual disk.

Users can backup their data to the virtual disk

via VDIVDI provides users with general file copy and

delete operations

users can regard the virtual disk as a ordinary

storage volume


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Recovery Manager : communicates with PCS

server in the cloud for data recovery.

Recovery Managers in the VDPG and the PCS

server collaborates both to generate parityblocks for each data block in the group and to

recover a data block in the group


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Storage Manager : creates and manages virtual

disk

It stores data blocks from the VDI to the virtual

disk reads data blocks for Recovery Manager

maintains disk metadata and file metadata

The PCS server generates parity groups for each

virtual disk


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It maintains metadatafor each VDPG

Metadata,group ID, IP address of each member

machine and accounting information of each

member collaborates with Recovery Managers to

generate parity blocks

stores the parity block to the cloud storage.


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In this section there are three process

1. Initial Parity Generation2. Parity Block Update

3. Data Block Recovery


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The only operation used for parity generation

and data recovery is Exclusive-OR

(XOR), which is a simple mixing function in

cryptography XOR operation

AA=0 and A+0=A


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(((((r S1) S2) S3) S4) r= S1 S2 S3 S4)

Final parity block = S1 S2 S3 S4

The initialization process occurs only once for

each parity group seed block is stored in the metadata region of

each virtual disk


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The Storage Manager in PCS agent maintains

parity generation bitmap (PG-bitmap)

The bitmap is initialized (set to 0) after the

initialization processZeroindicates that parity block is not generated

for data block

Parity block for the data block is updated

corresponding parity block in PCS also beupdated


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When a block (Bold) in node I is to be updated

to a new block (Bnew)

Storage Manager refers to the corresponding

value in the PG-bitmap If it is 0 then the Storage Manager generates an

intermediate parity block (Pt)

(Pt= Bnew Si) set PG Bitmap to 1

(Pt= Bnew Bold)


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Recovery Manager sends an update request

message

it contains the updated block # and Pt, to the

PCS server an update request message arrives from node I

PCS server identifies to which group node I

belongs and refers to the PG-bitmap of the

group


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If it is zero, PCS server generates the parity

block (Pnew)

(Pnew= PtPs)

(Pnew= PtPold)


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When a data block is corrupted the block can

be recovered using the parity block provided by

the PCS server

Assume that the n-th data block in node i hasbeen corrupted, Bin

Upon receiving message,PCS server identifies

the VDPG group

It generates Pr=Pn+r (if group size is even) Pr=Pn (if group size is odd)

Each node generates Ej=Bjn + r


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Bin = Pr E1 Ei-1 Ei+1 E|VDPG|


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A node can belong to multiple VDPGs for higher

recoverability and faster recovery time

As more vdpgs a node belongs to, the service

cost increasesAs the group size increases, the service cost

decreases

The recoverability and recovery time become

worse


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Namely, there is a tradeoff between the

efficiency (recoverability + recovery time) of the

PCS and its service cost

It is important to decide both the number ofgroups for a node and the group size,

appropriately

For faster recovery time, it is recommended to

select nodes with the same time zone


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Parity Cloud Service: A Privacy-Protected Personal Data

Recovery Service by Chi-won Song, Sungmin Park, Dong-wook Kim, Sooyong Kang

2011 International Joint Conference of IEEE TrustCom-11/IEEE ICESS-

11/FCST-11

Cloud Security Alliance, Security Guidance for Critical

Areas ofFocus in Cloud Computing, 2011.


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Parity Cloud Service

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