A followup question - if I disable write access to Fedora for say 5 to 10 minutes and then do the copy, what would happen if a client process was in the middle of an ingest operation?  Would it just pause until writes were re-enabled or throw an error?  



From: Edwin Shin <eddie@fedora-commons.org>
To: "Support and info exchange list for Fedora users." <fedora-commons-users@lists.sourceforge.net>
Cc: Christopher Emmerich <emmerichc@usgs.gov>
Date: 01/27/2012 02:09 PM
Subject: Re: Using rsync to replicate triplestore





I was recently working with various scenarios for Fedora replication in addition to Fedora's Journaling. I'm not familiar with AFS, but if you can take advantage of some sort snapshotting facility of your filesystem or volume manager, (e.g. as provided by ZFS or LVM) that might do the trick.

Alternatively: you say you can't shut down the master, but can you have Fedora refuse write operations for some window of time while you perform the rsync? If so, you could deny API-M operations by a policy while you rsync the Mulgara indices. See:
https://wiki.duraspace.org/pages/viewpage.action?pageId=27001135

fyi, Christopher, you should be directing your emails to fedora-commons-users@lists.sourceforge.net, not owner. I originally just hit reply and sent the message right back to owner and only now noticed it never went to the list.

On 27 Jan 2012, at 6:40 AM, Christopher Emmerich wrote:

>
> I'm looking for ideas here.  For various reasons, I can't use the standard replication methodology for creating and maintaining duplicate copies of my Fedora Commons repository.  Instead, the master server stores the Fedora data and Solr index files in read/write AFS directories, while the replicate servers access these directories via a read-only copy on redundant AFS storage.   This doesn't work for the Triplestore, however, because Mulgara requires read/write access.  Instead I've tried to do a nightly rsync of the leader triplestore index files to local disk on the Fedora replicates.  This only works if none of the master files are modified while the rsync is occurring.  Otherwise I get errors about out of sync records when I try to restart the Tomcat server on the replicate.  I can't shut the master server down while I do the rsync so I'm wondering if there are any other ways to accomplish this file transfer.