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From Todd Lipcon <>
Subject Re: cassandra vs hbase summary (was facebook messaging)
Date Mon, 22 Nov 2010 21:52:07 GMT
On Mon, Nov 22, 2010 at 1:26 PM, Edward Capriolo <>wrote:

> For cassandra all writes must be transmitted to all replicas.
> CASSANDRA-1314 does not change how writes happen. Write operations
> will still effect cache (possibly evicting things if cache is full).
> Reads however will prefer a single node of it's possible replicas.
> This should cause better cache utilization and less duplication for
> those using READ.ONE with lower read repair settings.
> It is also worth pointing out that the HBase cache is on entire hdfs
> blocks,

Nope, the HBase cache is on HFile blocks, which are typically 64KB.

> while Cassandra can cache on keys (key cache) or a key and all
> it's columns (row cache). This has some deep implications based on how
> random your reads are. Even with Cassandra's normal cache duplication
> having more fined grained caches, of or rows rather then blocks, could
> mean that they are more efficient anyway.

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