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From Chris Goffinet ...@chrisgoffinet.com>
Subject Re: Massive writes when only reading from Cassandra
Date Sat, 10 Sep 2011 22:04:14 GMT
You could tail the commit log with `strings` to see what keys are being
inserted.

On Sat, Sep 10, 2011 at 2:24 PM, Jonathan Ellis <jbellis@gmail.com> wrote:

> Two possibilities:
>
> 1) Hinted handoff (this will show up in the logs on the sending
> machine, on the receiving one it will just look like any other write)
>
> 2) You have something doing writes that you're not aware of, I guess
> you could track that down using wireshark to see where the write
> messages are coming from
>
> On Sat, Sep 10, 2011 at 3:56 PM, Jeremy Hanna
> <jeremy.hanna1234@gmail.com> wrote:
> > Oh and we're running 0.8.4 and the RF is 3.
> >
> > On Sep 10, 2011, at 3:49 PM, Jeremy Hanna wrote:
> >
> >> In addition, the mutation stage and the read stage are backed up like:
> >>
> >> Pool Name                    Active   Pending   Blocked
> >> ReadStage                        32       773         0
> >> RequestResponseStage              0         0         0
> >> ReadRepairStage                   0         0         0
> >> MutationStage                   158    525918         0
> >> ReplicateOnWriteStage             0         0         0
> >> GossipStage                       0         0         0
> >> AntiEntropyStage                  0         0         0
> >> MigrationStage                    0         0         0
> >> StreamStage                       0         0         0
> >> MemtablePostFlusher               1         5         0
> >> FILEUTILS-DELETE-POOL             0         0         0
> >> FlushWriter                       2         5         0
> >> MiscStage                         0         0         0
> >> FlushSorter                       0         0         0
> >> InternalResponseStage             0         0         0
> >> HintedHandoff                     0         0         0
> >> CompactionManager               n/a        29
> >> MessagingService                n/a      0,34
> >>
> >> On Sep 10, 2011, at 3:38 PM, Jeremy Hanna wrote:
> >>
> >>> We are experiencing massive writes to column families when only doing
> reads from Cassandra.  A set of 5 hadoop jobs are reading from Cassandra and
> then writing out to hdfs.  That is the only thing operating on the cluster.
>  We are reading at CL.QUORUM with hadoop and have written with CL.QUORUM.
>  Read repair chance is set to 0.0 on all column families.  However, in the
> logs, I'm seeing flush after flush of memtables and compactions taking
> place.  Is there something else that would be writing based on the above
> description?
> >>>
> >>> Jeremy
> >>
> >
> >
>
>
>
> --
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of DataStax, the source for professional Cassandra support
> http://www.datastax.com
>

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