Significant drop in storage load after 2.1.6->2.1.8 upgrade

[Mike Heffner]

Hi all,

I've been upgrading several of our rings from 2.1.6 to 2.1.8 and I've
noticed that after the upgrade our storage load drops significantly (I've
seen up to an 80% drop).

I believe most of the data that is dropped is tombstoned (via TTL
expiration) and I haven't detected any data loss yet. However, can someone
point me to what changed between 2.1.6 and 2.1.8 that would lead to such a
significant drop in tombstoned data? Looking at the changelog there's
nothing that jumps out at me. This is a CF definition from one of the CFs
that had a significant drop:

> describe measures_mid_1;

CREATE TABLE "Metrics".measures_mid_1 (
    key blob,
    c1 int,
    c2 blob,
    c3 blob,
    PRIMARY KEY (key, c1, c2)
) WITH COMPACT STORAGE
    AND CLUSTERING ORDER BY (c1 ASC, c2 ASC)
    AND bloom_filter_fp_chance = 0.01
    AND caching = '{"keys":"ALL", "rows_per_partition":"NONE"}'
    AND comment = ''
    AND compaction = {'class':
'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy'}
    AND compression = {'sstable_compression':
'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND dclocal_read_repair_chance = 0.1
    AND default_time_to_live = 0
    AND gc_grace_seconds = 0
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.0
    AND speculative_retry = '99.0PERCENTILE';

Thanks,

Mike

-- 

  Mike Heffner <m...@librato.com>
  Librato, Inc.