Well I just found this: http://wiki.apache.org/cassandra/LiveSchemaUpdates
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!" :-) Dave On Tue, Apr 3, 2012 at 6:00 PM, David Leimbach <leim...@gmail.com> 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 > > >
