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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9621) Repair of the SystemDistributed keyspace creates a non-trivial amount of memory pressure
Date Mon, 22 Jun 2015 08:27:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9621?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14595491#comment-14595491
] 

Sylvain Lebresne commented on CASSANDRA-9621:
---------------------------------------------

I don't particularly care if we make CASSANDRA-5839 opt-in or not, but I do think this issue
shouldn't weight much in that decision. As Markus said, this would still hurt people enabling
it and it's not gonna be clear at all that opting-in for CASSANDRA-5839 buys you into this.

Anyway, the patch is very simple and I don't think it's a big deal if we want to undo it later
so I'm not too fussed about this issue but I'm personally +1 on Marcus' patch (though I'd
add a comment pointing to this issue so we remember why we're doing this). 

> Repair of the SystemDistributed keyspace creates a non-trivial amount of memory pressure
> ----------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-9621
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9621
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Sylvain Lebresne
>            Assignee: Marcus Eriksson
>            Priority: Minor
>             Fix For: 2.2.0 rc2
>
>
> When a repair without any particular option is triggered, the {{SystemDistributed}} keyspace
is repaired for all range, and in particular the {{repair_history}} table. For every range,
that table is written and flushed (as part of normal repair), meaning that every range triggers
the creation of a new 1MB slab region (this also triggers quite a few compactions that also
write and flush {{compaction_progress}} at every start and end).
> I don't know how much of a big deal this will be in practice, but I wonder if it's really
useful to repair the {{repair_*}} tables by default so maybe we could exclude the SystemDistributed
keyspace from default repairs and only repair it if asked explicitly?



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