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From "Ryan Svihla (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-10013) Default commitlog_total_space_in_mb to 4G
Date Wed, 26 Aug 2015 12:16:46 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-10013?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14713012#comment-14713012
] 

Ryan Svihla edited comment on CASSANDRA-10013 at 8/26/15 12:16 PM:
-------------------------------------------------------------------

Only negative and I've hit this, is the commit log filling up a small partition that previously
was large enough. While I can safely say this should NEVER be a problem, it sometimes is and
affects 'small deployments' like some of the smaller cloud instances (EC2 m3.medium for example
is only 4g).

On the positive side:
  - better default performance (better out of the box experience for most customers)

On the negative side:
  - will block some new users from even using Cassandra ( new to cloud and new to Cassandra
I'd think )
  - May break some existing 2.1.x deployments who are just relying on default (most) and have
a tiny partition for commit log (I'd hope very very few)

If we go this route we need to make sure the minimum requirements are updated in the docs
and wiki correspondingly. It is also surprising in a point release to change a default.

EDIT: I also agree the configuration have a comment different than the default is HYPER surprising
and would be the first time I've even seen that in the wild.


was (Author: rssvihla):
Only negative and I've hit this, is the commit log filling up a small partition that previously
was large enough. While I can safely say this should NEVER be a problem, it sometimes is and
affects 'small deployments' like some of the smaller cloud instances (EC2 m3.medium for example
is only 4g).

On the positive side:
  - better default performance (better out of the box experience for most customers)

On the negative side:
  - will block some new users from even using Cassandra ( new to cloud and new to Cassandra
I'd think )
  - May break some existing 2.1.x deployments who are just relying on default (most) and have
a tiny partition for commit log (I'd hope very very few)

If we go this route we need to make sure the minimum requirements are updated in the docs
and wiki correspondingly. It is also surprising in a point release to change a default.

> Default commitlog_total_space_in_mb to 4G
> -----------------------------------------
>
>                 Key: CASSANDRA-10013
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-10013
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Config
>            Reporter: Brandon Williams
>             Fix For: 2.1.x
>
>
> First, it bothers me that we default to 1G but have 4G commented out in the config.
> More importantly though is more than once I've seen this lead to dropped mutations, because
you have ~100 tables (which isn't that hard to do with OpsCenter and CFS and an application
that uses a moderately high but still reasonable amount of tables itself) and when the limit
is reached CLA flushes the oldest tables to try to free up CL space, but this in turn causes
a flush stampede that in some cases never ends and backs up the flush queue which then causes
the drops.  This leaves you thinking you have a load shedding situation (which I guess you
kind of do) but it would go away if you had just uncommented that config line.



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