On Feb 8, 2012, at 10:31 AM, Adeel Qureshi wrote: > I have been using solr for a while and have recently started getting into > solrcloud .. i am a bit confused with some of the concepts .. > > 1. what exactly is the relationship between a collection and the core .. > can a core has multiple collections in it .. in this case all collections > within this core will have the same schema .. and i am assuming all > instances of collections within the core can be deployed on different solr > nodes to achieve distributed search .. > or is it the other way around where a collection can have multiple cores
Currently, a core basically equals a replica of the index. So you might have a collection called collection1 - lets say it's 2 shards and each shard has a single replica: Collection1 shard1 replica1 shard1 replica2 shard2 replica1 shard2 replica2 Each of those replicas is a core. So a collection has multiple cores basically. Also, each of those cores can be on a different machine. So yes, you have distributed indexing and distributed search. > > 2. at some places it has been pointed out that solrcloud doesnt actually > supports replication .. but in the solrcloud wiki the second example is > supposed to be for replication .. so does solrcloud at this point supports > automatic replication where as you add more servers it automatically uses > the additional servers as replicas SolrCloud doesn't support the old style Solr replication concept. It does however, handle replication - it's just all pretty much automatic and behind the scenes - eg all the information about Solr replication in the wiki documentation for previous versions of Solr is really not applicable. We now achieve replica copies by sending documents to each shard one document at a time so that we can support near realtime search. The old style replication is only used in recovery, or when you start a new replica machine and it has to 'catchup' to the other replicas. > > I have a few more questions but I wanted to get these basic ones out of the > way first .. I would appreciate any response. Fire away. > > Thanks > Adeel - Mark Miller lucidimagination.com
