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From "Maxim Podkolzine (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-9018) Dropped keyspace is not collected
Date Tue, 24 Mar 2015 13:42:53 GMT


Maxim Podkolzine commented on CASSANDRA-9018:

I see, thanks for clarification. Here's I find misleading here:
- The two settings are obviously conflicting. I personally find gc_grace_seconds option a
better choice, because it gives a sense of control: I can decide the expiration of my data,
per table on top of that.
- More general: there are several notions dealing with the same problem: grace period, snapshot
and backup. In such cases conflicts often arise.
- Strong recommended settings ("auto_snapshot: true") require an operator to monitor the disk
space. It seems more convenient if Cassandra takes care of its own space.
- The log doesn't give enough information about what's going on.

Can advise the proper settings for our case: it's perfectly normal that the data is dropped,
and it should be kept _just in case_ for some period? When needed we do a full backup ourselves.
Are there any potential problems with "auto_snapshot: false"?

> Dropped keyspace is not collected
> ---------------------------------
>                 Key: CASSANDRA-9018
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Maxim Podkolzine
>         Attachments:
> As far as I understand when a keyspace is dropped, the data is marked as tombstone. We
expect that after the grace period (all tables are created with gc_grace_seconds=7200), this
data is automatically removed during the compaction process, which means that keyspace no
longer takes any space on disk.
> This is not happening (not after 2 or 24 hours). The log keeps saying "No files to compact
for user defined compaction", keyspace files remain on disk. It's not clear whether Cassandra
is still waiting for certain event, or decided not to collect the data.
> Is there any setting that I missed? Any clues to figure out from the log, what's the
current state.

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