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From David Leimbach <>
Subject Re: System keyspace leak?
Date Wed, 04 Apr 2012 01:14:27 GMT
Well I just found this:

which explains a ton...  It looks like this particular Column Family will
grow infinitely (it's just one row with a column per migration), so if I'm
pounding on my Cassandra node with CREATE/DROP activity, I'm going to make
VERY wide row.

That tells me enough to say "don't do that!"  :-)


On Tue, Apr 3, 2012 at 6:00 PM, David Leimbach <> wrote:

> I've been trying to understand the overhead of create/drop keyspace on
> Cassandra 1.0.8.  It's not free, especially when I've managed to drive up
> the LiveDiskSpaceUsed for the Migrations CF in the "system" keyspace up to
> over 12 MB of disk.
> I've tried doing "nodetool -h localhost repair system" and other nodetool
> commands to try to compact the SSTables involved with it, but it never
> wants to let go of that slowly growing space.
> The Cassandra node in question is in a ring of size 1.
> Other than clobbering my data directory, how do I get my space back?  Is
> it natural for this to grow seemingly infinitely (even though it's pretty
> small increments), or did I find a bug?
> The reason I ask is I need to run unit tests in a shared developer
> infrastructure with Cassandra, and we were having a little trouble with
> TRUNCATE on column families, but that might have been environmental (I've
> not looked deeply into it).
> Which is less expensive?  Create/Drop, or Truncate?  I don't expect
> Truncate to swell the Migration Column Family because it tracks (seemingly)
> schema changes.
> Dave

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