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From "David Boxenhorn (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-2006) Serverwide caps on memtable thresholds
Date Tue, 25 Jan 2011 09:18:44 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2006?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12986286#action_12986286
] 

David Boxenhorn commented on CASSANDRA-2006:
--------------------------------------------

I guess that what my suggestion means, in practice, is that "the memtable in the system that
was using the largest fraction of it's local threshold would be flushed" would be applied
when a keyspace threshold is exceeded, rather than when a system threshold is exceeded.

When a server threshold is exceeded, you would first look for the keyspace that is using the
largest fraction of its threshold, then flush the memtable in that keyspace that is using
the largest fraction of its local threshold.

> Serverwide caps on memtable thresholds
> --------------------------------------
>
>                 Key: CASSANDRA-2006
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2006
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Stu Hood
>             Fix For: 0.8
>
>
> By storing global operation and throughput thresholds, we could eliminate the "many small
memtables" problem caused by having many CFs. The global threshold would be set in the config
file, to allow different classes of servers to have different values configured.
> Operations occurring in the memtable would add to the global counters, in addition to
the memtable-local counters. When a global threshold was violated, the memtable in the system
that was using the largest fraction of it's local threshold would be flushed. Local thresholds
would continue to act as they always have.
> The result would be larger sstables, safer operation with multiple CFs and per node tuning.

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