Automated P 2 P Backup Group 1 Anderson

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Automated P 2 P Backup Group 1 Anderson, Bowers, Johnson, Walker

Motivation • • Hard drive space is cheap Network connectivity is cheap Losing data is expensive We’d like to pool our resources and easily collectively maintain backups

Background – Distributed Hashes • Most academic P 2 P systems are built on “distributed hash tables” – Ask “the system” for a key, and get the content back • How the Distributed Hash and the hash lookup is implemented characterizes the P 2 P system

Related Work – P 2 P • Pastry – Each node has an ID, messages routed to node nearest the hash key – N-order graph used to route • Ocean. Store – Write-once, has versioning – Emphasizes local storage

Related Work – P 2 P (cont. ) • CHORD – Routes similarly to Pastry – Circular routing space • Freenet – Write-once – Many security and anonymity features • All resource encrypted by their hash key

Related Work – Distributed Backup • Distributed Internet Backup System – Not P 2 P – uses direct connections – Encrypts user data on other drives • Pastiche – Built on Pastry • PAST – Also built on Pastry • p. Store – Uses own P 2 P architecture

Design

P 2 P Adapter • Abstracts interfacing with a P 2 P system’s distributed hash • Writing another adapter could make this work with another system • We used Freenet because it is the only working P 2 P system publicly available • When backing up a file, returns a key that the adapter can later use to retrieve the file – P 2 P system specific – Freenet example: SSK@iuhgwe 78 gfq 93 f 73 f: /something/path/file. txt • Done in Python

Engine • Implements backup and retrieval logic • Drives the P 2 P adapter to insert and retrieve files • Stores keys from P 2 P adapter for retrieval • Done in Java

UI • Allows the user to select files or directories for backup % mark_dir > backup > done • Allows user to initiate backup or retrieval based on selection • Stores selections in “backup. txt” as a commadelimited file storing the filename, date of last backup, and retrieval key (if any) • Done in Java

Example Run bowersj 2@arctic> ls –l total 8 drwx-----2 bowersj 2 student 4096 Apr 16 13: 58 dir -rw------1 bowersj 2 student 27 Apr 16 13: 58 example bowersj 2@arctic> java Backup_UI % mark_dir > done % mark_file > example > done % backup Backing up dir/one. . . retrieval key freenet: SSK@iuhgwe 78 gfq 93 f 73 f/3 Backing up dir/two. . . retrieval key freenet: SSK@iuhgwe 78 gfq 93 f 73 f/4 Backing up example. . . retrieval key freenet: SSK@iuhgwe 78 gfq 93 f 73 f/5 % exit

Results • One limit of the Freenet library used was that files must be no larger then 64 KB • Not fundamental to Freenet • A Freenet file takes approximately 4 -5 seconds to insert into the system • Retrieval was very fast since it was always from the local drive cache

Design Benefits • Careful design allows each component to be implemented in any language • UI and Engine communicate through backup. txt • Engine and P 2 P adapter communicate through command lines • Problems getting other P 2 P systems running • Most not publicly available yet • PASTRY could not be compiled • Shipped source had Java exception handling errors

Conclusion • Modern P 2 P systems will provide a good substrate for this sort of application • When they are released and working! • Writing a basic version of this kind of application is fairly easy • Effectiveness depends on the underlying P 2 P system • Freenet doesn’t chunk files, some P 2 P systems do • Freenet has no retention guarantees, some P 2 P systems do • Freenet natively prevents snooping by other users, some P 2 P systems don’t

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