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From Karl Hiramoto <k...@hiramoto.org>
Subject Re: reducing disk usage advice
Date Sun, 13 Mar 2011 20:59:32 GMT
On 3/13/2011 9:27 PM, aaron morton wrote:
> The CF Stats are reporting you have 70GB total space taken up by 
> SSTables, of which 55GB is live. The rest is available for deletion, 
> AFAIK this happens when cassandra detects free space is running low. 
> I've never dug into how/when this happens though. 
If there was a way to force this deletion it would be nice.

du -hs data/
78G     data/

> With that amount of data it seems odd to fill a  300GB space during 
> repair or compaction. Some thoughts:
>
I maybe have 50 to 100GB of  other stuff including mysql and the OS 
(RHEL 5.5).   So about 200GB for cassandra

> - What version are you using ? There were issues in early 0.7 that 
> resulted in a lot of temp files been left around.
0.7.3

> - Take a look on disk. In the commit log directory are there a lot of 
> files hanging around? In the data directory for your keyspace do you 
> have any snapshots ? Is there anything in the saved caches directory?

No snapshots and not much other stuff

du -h saved_caches/
52K     saved_caches/

  du -h commitlog/
218M    commitlog/


no snapshots
> - When you've ran out of space what did the data directory look like ? 
> How did you fix the issue?
>
data directory had nearly 200GB of stuff.   When i kill  and restart the 
cassandra process data dir goes down to 60GB or so.    I can do the same 
if i do a "Force GC"  in jconsole.  A few days ago i asked if anyone 
knew how to force the GC  in a cron job and got no response.

http://wiki.apache.org/cassandra/FAQ#cleaning_compacted_tables
After compaction is done I have lots of extra SSTables laying around and 
it seems the only way to get rid of them is restarting cassandra, or 
jconsole GC.   I'd like a better way to automate it than restarting 
cassandra.


If at all possible I'd like to somehow be able to cleanup these files 
without paying for more storage of files I don't need.

Thanks,

Karl



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