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From Peter Schuller <>
Subject Re: GC Storm
Date Sun, 13 Jun 2010 09:08:05 GMT
> We've also seen similar problems

To be clear though; un-*flushed* data is very different from
un-*compacted* data and the above seems to be about unflushed data?

In my test case there was no problem at all flushing data. But my test
was sustained write speeds up to 200 million rows and ~ 200 gb of
space, and as the database grew larger the compaction goes goes up (as

For that particular workload it would probably have been beneficial to
have a configurable concurrency on compactions as well (similar to how
it is configurable for sstable flushing) because CPU was the
bottleneck in the compaction process (i.e., after stopping inserts and
letting compaction complete in the background, the compaction thread
was CPU-bound and there was plenty of available I/O capacity).

/ Peter Schuller

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