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From "Tyler Hobbs (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-6109) Consider coldness in STCS compaction
Date Wed, 23 Oct 2013 17:33:44 GMT


Tyler Hobbs commented on CASSANDRA-6109:

On second thought, filtering *buckets* (my misinterpretation of your statement) would be very
conservative and would generally have little effect since there is no control over what sstables
form buckets.

Here's my latest proposal: ignore the coldest SSTables until they (collectively) make up more
than X% of the total reads/key/sec.

This is pretty easy to tune and it handles all of the corner cases we've considered.  A conservative
default might be 1 to 5%.

> Consider coldness in STCS compaction
> ------------------------------------
>                 Key: CASSANDRA-6109
>                 URL:
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Tyler Hobbs
>             Fix For: 2.0.2
>         Attachments: 6109-v1.patch, 6109-v2.patch
> I see two options:
> # Don't compact cold sstables at all
> # Compact cold sstables only if there is nothing more important to compact
> The latter is better if you have cold data that may become hot again...  but it's confusing
if you have a workload such that you can't keep up with *all* compaction, but you can keep
up with hot sstable.  (Compaction backlog stat becomes useless since we fall increasingly

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