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From Ken Hancock <>
Subject Re: Why Solandra stores Solr data in Cassandra ? Isn't solr complete solution ?
Date Mon, 30 Sep 2013 17:35:55 GMT
To clarify, solr indexes are not distributed in the same way that Cassandra
data is stored.

With Cassandra, each node receives a fraction of the keyspace (based on
your replication factor and token assignment).  With DSE Search, writes to
Cassandra are hooked and each node independently indexes its data and keeps
this index on the local file system.  If you have keyspace with RF=3 then
three nodes will index each document. Indexes, unlike from Solr, only store
the docids and the actual field values are stored in Cassandra.

When it comes to search, DSE splits up the search so in the example above
only one of those RF=3 nodes will be queried for a particular token range
so that data can be unioned across all the nodes with different token

Not sure about Solandra, but you do need to be aware that there's a number
of Solr search options that are not supported on distribute searches/DSE

Also, be aware that while Cassandra has knobs to allow you to get
consistent read results (CL=QUORUM), DSE Search does not. If a node drops
messages for whatever reason, outtage, mutation, etc. its solr indexes will
be inconsistent with other nodes in its replication group.

On Mon, Sep 30, 2013 at 1:06 PM, Robert Coli <> wrote:

> On Mon, Sep 30, 2013 at 8:50 AM, Ertio Lew <> wrote:
>> Solr's data is stored on the file system as a set of index files[
>>]. Then why do we need anything
>> like Solandra or DataStax Enterprise Search? Isn't Solr complete solution
>> in itself ?  What do we need to integrate with Cassandra ?
> Solr's index sitting on a single machine, even if that single machine can
> vertically scale, is a single point of failure.
> The value add of DES is that the index has the same availability
> characteristics as the underlying data, because it is stored in the same
> cluster.
> =Rob

*Ken Hancock *| System Architect, Advanced Advertising
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