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diff --git a/src/mem3/README.md b/src/mem3/README.md deleted file mode 100644 index 8098f6979..000000000 --- a/src/mem3/README.md +++ /dev/null @@ -1,43 +0,0 @@ -## mem3 - -Mem3 is the node membership application for clustered [CouchDB][1]. It is used -in CouchDB since version 2.0 and tracks two very important things for the -cluster: - - 1. member nodes - 2. node/shards mappings for each database - -Both the nodes and shards are tracked in node-local couch databases. Shards -are heavily used, so an ETS cache is also maintained for low-latency lookups. -The nodes and shards are synchronized via continuous CouchDB replication, -which serves as 'gossip' in Dynamo parlance. The shards ETS cache is kept in -sync based on membership and database event listeners. - -A very important point to make here is that CouchDB does not necessarily -divide up each database into equal shards across the nodes of a cluster. For -instance, in a 20-node cluster, you may have the need to create a small -database with very few documents. For efficiency reasons, you may create your -database with Q=4 and keep the default of N=3. This means you only have 12 -shards total, so 8 nodes will hold none of the data for this database. Given -this feature, we even shard use out across the cluster by altering the 'start' -node for the database's shards. - -Shards can be split using the `/_reshard` API endpoint. Refer to a separate -[README](README_reshard.md) regarding the technical detail on how shard -splitting works. - -### Getting Started - -Mem3 requires R13B03 or higher and can be built with [rebar][2], which comes -bundled in the repository. Rebar needs to be able to find the `couch_db.hrl` -header file; one way to accomplish this is to set ERL_LIBS to point to the -apps subdirectory of a CouchDB checkout, e.g. - - ERL_LIBS="/usr/local/src/couchdb/apps" ./rebar compile - -### License -[Apache 2.0][3] - -[1]: http://couchdb.apache.org -[2]: http://github.com/rebar/rebar -[3]: http://www.apache.org/licenses/LICENSE-2.0.html |