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From eugene miretsky <eugene.miret...@gmail.com>
Subject Issues while using TWCS compaction and Bulkloader
Date Mon, 27 Mar 2017 22:26:55 GMT
Hi,

We have a Cassandra 3.0.8 cluster, and we use the Bulkloader
<http://www.datastax.com/dev/blog/using-the-cassandra-bulk-loader-updated>
to upload time series data nightly. The data has a 3day TTL, and the
compaction window unit is 1h.

Generally the data fits into memory, all reads are served from OS page
cache, and the cluster works fine. However, we had a few unexplained
incidents:

   1. High page fault ratio: The happened ones, for 3-4 days and was
   resolved after we restarted the cluster. Have not been able to reproduce it
   since.
   2. High Bloom number of bloom filter false positive: Same as above.

Several questions:

   1. What could have caused the page fault, and/or bloom filter false
   positives?
   2. What's the right strategy for running repairs?
      1. Are repairs even required? We don't generate any tombstones.
      2. The following article suggests that incremental repairs should not
      be used with Date Tiered compactions, does it also apply to TWCS?
      https://docs.datastax.com/en/cassandra/3.0/cassandra/operations/opsRepairNodesManualRepair.html

Cheers,
Eugene

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