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From Alain RODRIGUEZ <arodr...@gmail.com>
Subject Re: Even after the drop table, the data actually was not erased.
Date Fri, 12 Jan 2018 11:10:19 GMT
Hello,

However, the actual size of the data directory did not decrease at all.
> Disk Load monitored by JMX has been decreased.


This sounds like 'auto_snapshot' is enabled. This option will trigger a
snapshot before any table drop / truncate to prevent user mistakes mostly.
Then the data is removed but as it is still referenced by the snapshot
(hard link), space cannot be freed.

Running 'nodetool clearsnapshot' should help reducing the dataset size in
this situation.


The client fails to establish a connection and I see the following
> exceptions in the Cassandra logs.

org.apache.cassandra.db.UnknownColumnFamilyException: Couldn't find table
> for cfId…


This does not look like a failed connection to me but rather a try to query
some inexistent data. If that's the data you just deleted (keyspace /
table), this is expected. If not there is an other issue, I hope not
related to the delete in this case...

C*heers,
-----------------------
Alain Rodriguez - @arodream - alain@thelastpickle.com
France / Spain

The Last Pickle - Apache Cassandra Consulting
http://www.thelastpickle.com



2018-01-12 7:14 GMT+00:00 Eunsu Kim <eunsu.bill23@gmail.com>:

> hi everyone
>
> On the development server, I dropped all the tables and even keyspace
> dropped to change the table schema.
> Then I created the keyspace and the table.
>
> However, the actual size of the data directory did not decrease at all.
> Disk Load monitored by JMX has been decreased.
>
>
>
> After that, Cassandra does not work normally.
>
> The client fails to establish a connection and I see the following
> exceptions in the Cassandra logs.
>
> org.apache.cassandra.db.UnknownColumnFamilyException: Couldn't find table
> for cfId…….org.apache.cassandra.io.FSReadError: java.io.IOException:
> Digest mismatch exception……
>
>
> After the data is forcibly deleted, Cassandra is restarted in a clean
> state and works well.
>
> Can anyone guess why this is happening?
>
> Thank you in advance.
>

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