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From Fred Groen <fg91...@student.american.edu>
Subject Re: Cassandra compression not working?
Date Tue, 25 Sep 2012 02:02:05 GMT
You are going to need a fully optimized flux-capacitor for that.

On Tue, Sep 25, 2012 at 5:00 AM, Michael Theroux <mtheroux2@yahoo.com>wrote:

> Hello,
>
> We are running into an unusual situation that I'm wondering if anyone has
> any insight on.  We've been running a Cassandra cluster for some time, with
> compression enabled on one column family in which text documents are
> stored.  We enabled compression on the column family, utilizing the
> SnappyCompressor and a 64k chunk length.
>
> It was recently discovered that Cassandra was reporting a compression
> ratio of 0.  I took a snapshot of the data and started a cassandra node in
> isolation to investigate.
>
> Running nodetool scrub, or nodetool upgradesstables had little impact on
> the amount of data that was being stored.
>
> I then disabled compression and ran nodetool upgradesstables on the column
> family.  Again, not impact on the data size stored.
>
> I then reenabled compression and ran nodetool upgradesstables on the
> column family.  This resulting in a 60% reduction in the data size stored,
> and Cassandra reporting a compression ration of about .38.
>
> Any idea what is going on here?  Obviously I can go through this process
> in production to enable compression, however, any idea what is currently
> happening and why new data does not appear to be compressed?
>
> Any insights are appreciated,
> Thanks,
> -Mike

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