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From Benjamin Heiskell <bheisk...@datto.com>
Subject TWCS decommission and cleanups
Date Wed, 15 Nov 2017 15:57:33 GMT
Hello all,

How does TWCS work when decommissioning a node? Does the data distribute
across the other nodes to the current time window's sstable (like
read-repairs)? Or will it compact into the sstables for the prior windows?
If that's how it works, how does it decide what sstable to compact with?
E.g.., if I ran a major compaction on one node (pushing everything into a
few sstables), then decommissioned it, what would you expect to see on
other nodes? Would the data distribute across all sstables based on the
row's timestamp?

I'm also a little unclear on how cleanups work. If I run a nodetool
cleanup, will that actually re-write the old, but not completely expired
sstables of prior time windows? Or are those sstables truly immutable?

I've read through the documentation (
http://cassandra.apache.org/doc/latest/operating/compaction.html#time-window-compactionstrategy)
and a few other resources (
http://thelastpickle.com/blog/2016/12/08/TWCS-part1.html), but I still
don't have a clear understanding of how it works.

Any clarification would be greatly appreciated. Thanks!
Ben

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