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From aaron morton <>
Subject Re: SSTable compaction issue in our system
Date Tue, 24 Jan 2012 08:25:18 GMT
When the default compaction strategy the SSTables are grouped into buckets, where the size
of every sstable int he bucket is within 50% of the average size of files in the bucket. There
is also a catch all first bucket for all files less than 50MB (by default). 

The min_compaction_threshold CF settings applies to the number of files in each bucket. 

So in your case you would have the following buckets:
- 4 * 50MB 
- 1 * 100MB
- 1 * 200MB 

It would compact the first bucket and create a file that would be in a bucket with one of
the other two files. 


Aaron Morton
Freelance Developer

On 24/01/2012, at 12:46 PM, Roshan wrote:

> Hi
> We have deployed two node Cassandra 1.0.6 cluster to production and it
> create SSTables on daily with different sizes. As I know, Cassandra will
> compact 4 (as default compaction threshold) same size files identified by
> compaction task. But every time in my system it identify 50MB 4 files and
> compact it to some size (e.g. 200MB) SSTable by removing tombstones. But
> next time it will compact 50MB 4 size file to another size (e.g. 100MB). If
> the compact task create such different size files after removing tombstones,
> some different size files are remain in system and not identified by
> compaction task. 
> I think major compaction using nodetool is not recommend for Cassandra 1.0.X
> versions. So could you pelase advice me how to combine different size
> SSTables together. Thanks. 
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