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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-6109) Consider coldness in STCS compaction
Date Wed, 02 Oct 2013 18:25:44 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13784245#comment-13784245
] 

Jonathan Ellis edited comment on CASSANDRA-6109 at 10/2/13 6:25 PM:
--------------------------------------------------------------------

I guess whether hotness or overlap is a more important criterion depends on your goal:
# prioritizing by hotness helps speed reads up more, especially when you have a lot of cold
data sitting around
# prioritizing by overlap ratio reduces disk space and helps throw away obsolete cells faster

I was hoping to tackle #1 here, but maybe that needs a separate strategy a la CASSANDRA-5561.

For #2, CASSANDRA-5906 adds a HyperLogLog component that does a fantastic job of letting us
estimate overlap ratios.




was (Author: jbellis):
I guess whether hotness or overlap is a more important criterion depends on your goal:
# prioritizing by hotness helps speed reads up more, especially when you have a lot of cold
data sitting around
# prioritizing by overlap ratio reduces disk space and helps throw away obsolete cells faster

I was hoping to tackle #1 here, but maybe that needs a separate strategy a la CASSANDRA-5560.

For #2, CASSANDRA-5906 adds a HyperLogLog component that does a fantastic job of letting us
estimate overlap ratios.



> 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
>
>
> 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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