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We have switched our searches to Solr since May 2010 and had no problem until about 1-2 months ago when replication goes really weird. We have 4 Slaves and 1 Master. The Slaves replicate at about 2-3 minutes (it is a really dynamic website so we need information to be available pretty fast to the user). Out index is 1.1Gb. When the replication starts it goes pretty fast (over 25mb/sec), but when it reaches 99%, speed starts to drop slowly and it finishes replication only when speed has dropped to a couple of kb/secs.