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From Brian Spindler <>
Subject TWCS Compaction backed up
Date Tue, 07 Aug 2018 23:38:12 GMT
Hey guys, quick question:

I've got a v2.1 cassandra cluster, 12 nodes on aws i3.2xl, commit log on
one drive, data on nvme.  That was working very well, it's a ts db and has
been accumulating data for about 4weeks.

The nodes have increased in load and compaction seems to be falling
behind.  I used to get about 1 file per day for this column family, about
~30GB Data.db file per day.  I am now getting hundreds per day at  1mb -

How to recover from this?

I can scale out to give some breathing room but will it go back and compact
the old days into nicely packed files for the day?

I tried setting compaction throughput to 1000 from 256 and it seemed to
make things worse for the CPU, it's configured on i3.2xl with 8 compaction


Lastly, I have mixed TTLs in this CF and need to run a repair (I think) to
get rid of old tombstones, however running repairs in 2.1 on TWCS column
families causes a very large spike in sstable counts due to anti-compaction
which causes a lot of disruption, is there any other way?

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