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From Julie <julie.su...@nextcentury.com>
Subject Re: Cassandra disk space utilization WAY higher than I would expect
Date Wed, 18 Aug 2010 15:35:12 GMT
Jonathan Ellis <jbellis <at> gmail.com> writes:

> 
> If you read the stack traces you pasted, the node in question ran out
> of diskspace.  When you have < 25% space free this is not surprising.
> 
> But fundamentally you are missing something important from your story
> here.  Disk space doesn't just increase spontaneously with "absolutely
> no activity."


I agree, it's not surprising for a node to run out of disk space when it is
occupying 122GB (133GB including the still present compacted files) on a 160GB
drive.  What I don't understand is how 30GB of data grew into 122GB.

I could send you the Cassandra log files from the time period after the 800,000
rows of writes complete.  There was no activity other than Cassandra doing
whatever work it does behind the scenes.

The 800,000 unique key writes started at 12:15pm and completed at 1:47pm.  These
8 vms were created solely for this test and I was the only one logged on.  After
the writes were done, Cassandra did what it does behind the scenes, there was no
human intervention and no clients running/connecting to it.  I didn't log in
again to check on things until 11pm that night which is when I saw the uneven
data distribution (122GB on one of the nodes).

I actually have the log files from all 8 nodes if it helps to diagnose what
activity was going on behind the scenes.  I really need to understand how this
happened.

Thanks again for your help,
Julie




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