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From Jean Tremblay <jean.tremb...@zen-innovations.com>
Subject Re: LeveledCompactionStrategy
Date Fri, 15 May 2015 06:23:08 GMT
Thanks a lot.
On 14 May 2015, at 22:45 , Nate McCall <nate@thelastpickle.com<mailto:nate@thelastpickle.com>>
wrote:

You can make LCS more aggressive with tombstone-only compactions via seting unchecked_tombstone_compaction=true
and turn down tombstone_threshold to 0.05 (maybe going up or down as needed). Details on both
can be found here: http://docs.datastax.com/en/cql/3.1/cql/cql_reference/compactSubprop.html

As for monitoring tombstones, there is a "tombstoneScannedHistogram" on ColumnFamilyMetrics
which measures how many tombstones were discarded during reads.

Also, you should take a couple of SSTables from production and use the sstablemetadata utility
specifically looking at "Estimated droppable tombstones" and "Estimated tombstone drop times"
output from such.

Spend some time experimenting with those settings incrementally. Finding the sweet spot is
different for each workload will make a huge difference in overall performance.



On Thu, May 14, 2015 at 8:06 AM, Jean Tremblay <jean.tremblay@zen-innovations.com<mailto:jean.tremblay@zen-innovations.com>>
wrote:
>
> Hi,
>
> I’m using Cassandra 2.1.4 with a table using LeveledCompactionStrategy.
> Often I need to delete many rows and I want to make sure I don’t have too many tombstones.
>
> How does one get rid of tombstones in a table using LCS?
> How can we monitor how many tombstones are around?
>
> Thanks for your help.
>
> Jean




--
-----------------
Nate McCall
Austin, TX
@zznate

Co-Founder & Sr. Technical Consultant
Apache Cassandra Consulting
http://www.thelastpickle.com<http://www.thelastpickle.com/>

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