Sergio Esteves created CASSANDRA-7453:
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Summary: Geo-replication in Cassandra
Key: CASSANDRA-7453
URL: https://issues.apache.org/jira/browse/CASSANDRA-7453
Project: Cassandra
Issue Type: Wish
Reporter: Sergio Esteves
Priority: Minor
Currently, a Cassandra cluster spanned across different datacenters replicates
all data to all datacenters when an update is performed. This is a problem for
the scalability of Cassandra as the number of datacenters increases.
It would be desirable to have some way to make Cassandra aware of the location
of data requests so that it could place replicas close to users and avoid
replicating to remote datacenters that are far away.
To this end, we thought of implementing a new replication strategy and some
possible solutions to achieve our goals are:
1) Using a byte from every row key to identify the location of the primary
datacenter where data should be stored (i.e., where it is likely to be
accessed).
2) Using an additional CF for every row to specify the origin of the data.
3) Replicating only to the 2 closest datacenters from the user (for reliability
reasons) upon a write update. For reads, a user would try to fetch data from
the 2 closest datacenters; if data is not available it would try the other
remaining datacenters. If data fails to be retrieved too many times, it means
that the client has moved to other part of the planet, and thus data should be
migrated accordingly. We could have some problems here, like having the same
rows, but with different CFs in different DCs (i.e., if users perform updates
to the same rows from different remote places).
What would be the best way to do this?
Thanks.
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