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From "Stu Hood (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-2006) Serverwide caps on memtable thresholds
Date Thu, 07 Apr 2011 06:29:05 GMT


Stu Hood commented on CASSANDRA-2006:

I'm very excited about this change: my last nitpick is that the flush_largest_memtables_at
and memtable_total_space_in_mb settings could be made more consistent. At the absolute minimum,
they should refer to one another in the config file, but I'm wondering how we might unify
the 3 or 4 different reasons for flushing in our monitoring/logging somehow.

Also, we should start making a plan to deprecate the per-cf settings, or convert them into
fractions as mentioned above.

> Serverwide caps on memtable thresholds
> --------------------------------------
>                 Key: CASSANDRA-2006
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Stu Hood
>            Assignee: Jonathan Ellis
>             Fix For: 0.8
>         Attachments: 2006-v2.txt, 2006-v3.txt, 2006.txt, jamm-0.2.jar
> 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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