By Ashok Kumar(Y2102)

File Synchronizer and Personal AssistanceBTP Project ReportBy: Ashok Kumar(Y2102)BTP Supervisor: Professor T.V Prabhakar{ashokk, tvp}@cse.iitk.ac.inDEPARTMENT OF COMPUTER SCIENCE ANDENGINEERINGINDIAN INSTITUTE OF TECHNOLOGY KANPURApril - 13, 2006AbstractFile synchronization, in its simplest form, is automatic updating files and directory from a specified directory on one system to the other system or within the system. Whenever changes are made, in files and/or directory, my tool then up to date it, according to the most recent modification date by propagating the changes in each replica and keeping the backup copy of the modified file into the specified directory.KEYWORD: File Synchronization, Time Synchronization1.0 IntroductionAnyone who uses more than one computer is aware of the data management problem posed by doing so: having multiple copies of files requires synchronization of files to bring all copies up to date after some copies have changed.The simplest and perhaps most widespread method is manual synchronization, in which users remember which files they have changed on which directory or computers and manually copy those files to the other directory or computers. Since users must manually keep track of which files are up-to-date and which are out-of-date, this method is highly error-prone.The better method is to use my tool “file synchronizers” which track changes to files, directory and propagate those changes from•Computer to USB hard disk and vise versa•Computer to Computer over the NetworkTo accomplish this first of all user must run my “Time Synchronization” tool to correct the system clock according to the “NTP” server of IITK, so that all the system within the IITK can be synchronize without time adjustment problem.Also my tools synchronized according to the modification time of the file which imposes one constraint: the user must remember to synchronize the computer whenever he switches from one to another. If he does not, he might end up with different new versions of the same file on different computer and will lose one change or the other.2.0 Problem Statement: SynchronizationFirst of all we must know what a correct synchronization must accomplish. A strict formal definition of correctness is an on going research topic (see, for example, Balasubramanian and Pierce [1], Pierce and Voilloun [2]), so we will make a informal definition as:“File synchronization, in its simplest form, is automatic updating files and directory from a specified directory on one system to the other system or within the system.”Also we consider a unidirectional synchronization, changes from one replica are propagated to a second, but changes on the second do not propagate back to the first. Bidirectional synchronizer can be easily built from two unidirectional synchronizer.We will call a unidirectional synchronization that propagates changes from A to B, leaving A unchanged, a “sync from A to B”.This section present the job of synchronization from two points of view:•First considering the synchronization of a single file and directory containing files with no sub-directory.•And then considering the synchronization of entire file and directory hierarchy.3.0 Synchronizing FilesTo decide how to synchronize individual files, file synchronizer must follow the “no lost updates rule”.3.1.0 No Lost UpdatesCorrect synchronization provides a “no lost updates” guarantee.Suppose each file is represented by the modifications time over the course of its lifetime, beginning with its initial creation. If two replicas have different copies of file (call the copies A and B), it is safe to replace A with B only if A’s modification time is more recent than B’s.Let F A and F B denotes the version of the file on A and BM A and M B denotes their modification times.Left_To_Right_Synchronization( A B) ≡if ( M A = M B ) // same modification time implies files are same(for{ //within the system)nothingdo}else if ( M A < M B ){do nothing // in bidirectional sync. F B will update A}else{F B to archive directory )Move(F A to BUpdate}Fig. 1: An algorithmic specification of single file synchronization in terms of modification time.3.1.1Synchronizing file systemFor synchronizing the file system we have to consider the subdirectories along with files. So when synchronizing from left to right and if right side do not contains the files and directories existing in the left then we are creating all the files and directories to the right. And if some files and directories with the name same as in the left exist to the right then we are updating it with the algorithm (mention in fig.1) by recursively calling the function.4.0 Solution overviewThe solution for the problem mention in section 2.0 can be solved through the tool provided by me and following the section 3.0 and its sub-section.5.0 Mile Stone AchievedThe tools provided by me are:•Time Synchronizer•Directories and File Synchronizer from system to USB hard drive and vise versa.•File Synchronizer from system to system over the network.5.1 Function of Tools•Time Synchronizer:This tool synchronizes the system clock according to the NTP server of iitk, so that there is no discrepancy between the system clocks within the domain for synchronization to take place and now if we run the “file synchronizer” we don’t have to bother about the time difference between the systems.It has been implemented according to RFC-2030 [3].Fig. 2: An algorithm for synchronizing time from the NTP server.•Directories and File Synchronizer from system to USB hard drive: This tool synchronizes the directories and files recursively from system to USB drive and vise versa taking modification date as a parameter. Also it keeps the backup copy of the replaced files in specified directory.Fig. 3: File Synchronization over view•File Synchronizer from system to system over the network:This tool synchronizes the files from system to system over the network taking modification date as a parameter and keeps the backup copy of the replaced files in specified directory.Fig. 4: File Synchronization over view over the networkAll the above mention tools has been developed for windows on dotNet platform and the implementation language is C#, which can solve the problem stated in the section (2.0).6.0 Final OutcomeOutcome of this semester BTP project is a GUI based tools implemented in C# on dotNetplatform for windows operating system to solve the file synchronization problem.7.0 Future work“Directories and File Synchronizer” from system to USB hard drive has beenimplemented completely but “File Synchronizer” over the network is only for fileswithin the directory. So in future it can be implemented for sub-directories within thedirectory and recursively.References[1] S. Balasubramanian and Benjamin C. Pierce. What is a file synchronizer? InProceedings of the Fourth Annual ACM/IEEE International Conference onMobile Computing and Networking (MobiCom ’98), October 1998.[2]Benjamin C. Pierce and Jerome Vouillon. What’s in Unison? A formalspecification and reference implementation of a file synchronizer. TechnicalReport MS-CIS-03-36, Dept. of CIS, University of Pennsylvania, 2004.[3] /rfcs/rfc2030.html[4] Fig.2 has been taken from section “SNTP Client Operations” of above link.。