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From Kevin Burton <bur...@spinn3r.com>
Subject 2x disk space required for full compaction? Don't vnodes help this problem?
Date Thu, 24 Jul 2014 21:56:27 GMT
I just bootstrapped a new node.

The box had about 220GB of data on it on a 400GB SSD drive.

I triggered a full compaction after it bootstrapped, and it ran out of disk
space about 15 minutes later.  so now that node is dead :-(

I would have assumed that vnodes meant that I could keep my drive near 100%
full…

so during a major compaction it would just compact the first vnode, then
move on to the second.

this would be analogous to bigtable / hbase regions.

but … that doesn't seem to be the case.  (so bad assumption on my part)
Both in terms of me actually seeing the disk fill up, and also the case of
my disk not having separate SSTables for each vnode.

So now I have these SSDs that I have to keep at > 50% capacity at all times.

I can see why on HDDs having too many files would be an issue.

But on SSDs this is less of a problem.

Perhaps some hybrid where vnodes are chunked together in one contiguous
region?

Is there a way to fix this problem? I would like to get more usage out of
my SSDs...

-- 

Founder/CEO Spinn3r.com
Location: *San Francisco, CA*
blog: http://burtonator.wordpress.com
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