@rbiswas, You may have read this but there's some good info here in what they describe as a "real world" production configuration using the new cross-data-center replication: https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=62687462 Since this feature only came out in 6.0 which was released less than 2 months ago, there's probably been limited production use. ALSO....Not a best practice, but since way before Solr Cloud existed, we used a brute force method of cross-data-center replication for stand-by Solrs with the magic of rsync. You can reliably use rsync to copy indexes as they are being updated, but there's a bit of scripting required. I have only done this in non-cloud environments, but I'm pretty sure it can be done in cloud as well. It is crude, but it worked for years and uses some of the great features of linux. Example script, run in crontab from the DR site nodes: #step 1 - create a backup first, assuming your current copy is good.
cp -rl ${data_dir} ${data_dir}.BAK
#step 2 - Now copy from the primary site
status=1
while [ $status != 0 ]; do
rsync -a --delete ${primary_site_node}:${data_dir} ${data_dir}
status=$?
done
echo "COPY COMPLETE!"
That script will create local backup (instantly via hard-links, not soft links) and then copies [only] new files and deletes files from DR that are have been deleted from Primary/remote. If files disappear during the rsync copy, it will copy again until nothing changes during the rsync. This can be run from crontab, but it does need a bit of bullet-proofing. Simple. Crude. It works.
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