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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6109) Consider coldness in STCS compaction
Date Sun, 20 Oct 2013 01:12:42 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13800057#comment-13800057
] 

Jonathan Ellis commented on CASSANDRA-6109:
-------------------------------------------

What if we just added a bucket filter that said, SSTables representing less than X% of the
reads will not be bucketed?  Straightforward to tune and I can't think of any really pathological
cases, other than where size-tiering just doesn't put hot overlapping sstables in the same
bucket.  (Which I think is out of scope to solve here -- we need cardinality estimation to
fix that.)

> Consider coldness in STCS compaction
> ------------------------------------
>
>                 Key: CASSANDRA-6109
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6109
>             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
behind.)



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