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From Mike <>
Subject Re: Cassandra compression not working?
Date Mon, 24 Sep 2012 21:14:31 GMT
I forgot to mention we are running Cassandra 1.1.2.


On Sep 24, 2012, at 5:00 PM, Michael Theroux <> 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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