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https://issues.apache.org/jira/browse/CASSANDRA-16071?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17197916#comment-17197916
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Scott Carey commented on CASSANDRA-16071:
-----------------------------------------

Heads-up for anyone currently working around this bug by setting the value in 
bytes.

With this bug fix, it appears we will need to change our config file or risk 
going OOM.  For me, it will go from a setting of 10MB to 10TB when the version 
is bumped if I don't change the config when updating.

> max_compaction_flush_memory_in_mb is interpreted as bytes
> ---------------------------------------------------------
>
>                 Key: CASSANDRA-16071
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-16071
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Feature/SASI
>            Reporter: Michael Semb Wever
>            Assignee: Michael Semb Wever
>            Priority: Normal
>             Fix For: 4.0, 3.11.8, 4.0-beta2
>
>
> In CASSANDRA-12662, [~scottcarey] 
> [reported|https://issues.apache.org/jira/browse/CASSANDRA-12662?focusedCommentId=17070055&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-17070055]
>  that the {{max_compaction_flush_memory_in_mb}} setting gets incorrectly 
> interpreted in bytes rather than megabytes as its name implies.
> {quote}
> 1.  the setting 'max_compaction_flush_memory_in_mb' is a misnomer, it is 
> actually memory in BYTES.  If you take it at face value, and set it to say, 
> '512' thinking that means 512MB,  you will produce a million temp files 
> rather quickly in a large compaction, which will exhaust even large values of 
> max_map_count rapidly, and get the OOM: Map Error issue above and possibly 
> have a very difficult situation to get a cluster back into a place where 
> nodes aren't crashing while initilaizing or soon after.  This issue is minor 
> if you know about it in advance and set the value IN BYTES.
> {quote}



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