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From Peter Schuller <>
Subject Re: No space left on device
Date Fri, 24 Dec 2010 10:46:23 GMT
>> In any case: Monitoring disk-space is very very important.
> So, why doesn't cassandra monitor it itself and stop accepting writes if it runs out
of space?

For one thing, it's non-trivial to do accurately because disk space
usage varies over time due to background compaction and/or
anti-compaction. Compaction will require different amount of
diskspaces depending on the nature of writes (e.g., if all writes are
removals compaction takes much less space than if all writes are
non-overwriting inserts).

Maybe the maximum possible disk space use can be kept track of in a
conservative fashion (assuming all writes are non-overwriting inserts,
assuming a maximally disk-space intensive repair will be run, etc) and
then behave appropriately based on that. If someone has a use case
where the cluster is sufficiently close to running out of disk space
(but it works for the particular use-case), such a feature could be
turned off. But it would make it less easy to accidentally write
yourself into a corner.

/ Peter Schuller

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