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From Yoshi Kimoto <yy.kim...@gmail.com>
Subject Re: When commitlog segment files are removed actually?
Date Thu, 08 Dec 2016 08:56:39 GMT
That is probably because the relevant memtable is flushed to SSTable and
the content of the commit log is not required any more so it's rewinding.

See:
http://docs.datastax.com/en/cassandra/3.x/cassandra/dml/dmlHowDataWritten.html



2016年12月8日(木) 17:45 Satoshi Hikida <sahikida@gmail.com>:

> Hi,
>
> I have a question about commit log.
>
> When commit log segment files are remove actually?
>
> I'm running a single node cluster for a few weeks to test C* performance.
> My simple test have been issuing only read and write requests to the
> cluster, then the data size (SSTables size) are increasing monotonously.
>
> Here are customized C* settings in my environment.
> - commitlog_total_space_in_mb: 8192
> - memtable_flush_writers: 4
> - memtable_heap_space_in_mb: 2048
>
> And here is the node specs used in my environment.
> - CPU core: 4
> - Memory: 16GB
> - SSD: 100GB * 2 (one for commit log, the other for data)
>
> In this case, I expected that the total size of the commit log segment
> files are increased up to 8GB. However, when the total size is
> increased up to 3GB, the commit log segment files are removed and
> total size reduced to around 250MB.
>
> I wonder why commit log segment files are removed before total size is
> increased up to 8GB(= commitlog_total_space_in_mb) ?  Could anyone give
> me some advices?
>
>
> Regards,
> Satosh
>
>
>
>

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