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From aaron morton <aa...@thelastpickle.com>
Subject Re: nodetool cleanup - results in more disk use?
Date Mon, 04 Apr 2011 11:57:14 GMT
cleanup reads each SSTable on disk and writes a new file that contains the same data with the
exception of rows that are no longer in a token range the node is a replica for. It's not
compacting the files into fewer files or purging tombstones. But it is re-writing all the
data for the CF. 

Part of the process will trigger GC if needed to free up disk space from SSTables no longer
needed.

AFAIK having fewer bigger files will not cause longer minor compactions. Compaction thresholds
are applied per bucket of files that share a similar size, there is normally more smaller
files and fewer larger files. 

Aaron

On 2 Apr 2011, at 01:45, Jonathan Colby wrote:

> I discovered that a Garbage collection cleans up the unused old SSTables.   But I still
wonder whether cleanup really does a full compaction.  This would be undesirable if so.
> 
> 
> On Apr 1, 2011, at 4:08 PM, Jonathan Colby wrote:
> 
>> I ran node cleanup on a node in my cluster and discovered the disk usage went from
3.3 GB to 5.4 GB.  Why is this?
>> 
>> I thought cleanup just removed hinted handoff information.   I read that *during*
cleanup extra disk space will be used similar to a compaction.  But I was expecting the disk
usage to go back down when it finished.
>> 
>> I hope cleanup doesn't trigger a major compaction.  I'd rather not run major compactions
because it means future minor compactions will take longer and use more CPU and disk.
>> 
>> 
> 


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