This illustrates the importance of NOT confusing *replication* for redundancy, whether that be rsync, LOCKSS, something SAN-based, etc, with *backups* for version retention, whether that be conventional weekly-full/daily-incr, snapshots, CDP, etc.
(It also illustrates the importance of validating checksums regularly!) This is the kind of thing Mark was getting at. SDR guidelines and good preservation policies should require redundancy for availability and/or disaster recovery, checksums (and periodic validation!) for integrity purposes, and backups for protection against human error and/or for disaster recovery. HOWEVER, implementing those things in a way that serves their preservation goals requires a sysadmin who understands those preservation goals. For example, ideally, backup or snapshot retention would be at least twice as long as the frequency with which checksums are validated, so that if a validation error is detected, you have at least two previous copies to go back to. Ultimately there is a level of detail below which local decisions on implementation are irrelevant--for example, the architecture of the backup system--but without some understanding of the preservation goals, a sysadmin is not guaranteed to make the right decision. Cory Snavely University of Michigan Library IT Core Services On Tue, 2007-02-20 at 09:30 +0000, Philip Adams wrote: > Hi, > > > > Checksums may be reassuring for checking that a file still has > integrity, but they leave open the question of what to do if the > checksums do not match. > > > > There is a growing movement of people interested in trying to ensure > that digital preservation techniques exist to overcome this problem. > One of the most interesting applications to come out of this is LOCKSS > (Lots of Copies Keeps Stuff Safe) see > http://www.lockss.org/lockss/Home for details. > > > > Most of the material archived using LOCKSS so far is from electronic > journals, with some government papers and the odd blog. LOCKSS acts as > a store, a proxy and a repairer. If applied to DSpace, it could enable > a kind of co-operative backup network to develop with copies of > content from repositories mirrored on a number of LOCKSS boxes. If > your DSpace was unable to deliver content it could be served up from > LOCKSS acting as a proxy instead. LOCKSS boxes spend much of their > time contacting each other to take part in integrity checking polls > and repairing content where required. > > > > There is a recent survey of the digital preservation strategies > available at the moment at > http://www.clir.org/pubs/reports/pub138/pub138.pdf. De Montfort > University is taking part in the UK LOCKSS Pilot programme: > http://www.jisc.ac.uk/whatwedo/programmes/programme_preservation/programme_lockss.aspx. > > > > Perhaps repository owners could use LOCKSS in either public or private > networks to look after the digital preservation aspects of managing > their content. > > > > Regards, > > Philip Adams > > Senior Assistant Librarian (Electronic Services Development) > > De Montfort University Library > > 0116 250 6397 > > > > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys-and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ DSpace-tech mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/dspace-tech ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ DSpace-tech mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/dspace-tech
