[
https://issues.apache.org/jira/browse/CASSANDRA-6357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13902294#comment-13902294
]
Aleksey Yeschenko commented on CASSANDRA-6357:
----------------------------------------------
Mostly LGTM.
Pushed a slightly tweaked version to
https://github.com/iamaleksey/cassandra/commits/6357, that:
- simplifies and fixes cassandra.yaml/Config/DD memtable_flush_writers
inconsistencies
- fixes the typo in Directories.getKSChildDirectories()
- makes AbstractCompactionTask.getWriteableLocation() consistent with
FlushRunnable.getWriteableLocation()
I have an issue with the naming in Directories with getWriteableLocation() vs.
getFlushLocation(). I think we should rename getWriteableLocation() to
something like getCompactionLocation(), to make the distinction between the two
clear.
Other than that +1.
> Flush memtables to separate directory
> -------------------------------------
>
> Key: CASSANDRA-6357
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6357
> Project: Cassandra
> Issue Type: New Feature
> Components: Core
> Reporter: Patrick McFadin
> Assignee: Jonathan Ellis
> Priority: Minor
> Fix For: 2.1
>
> Attachments: 6357-v2.txt, 6357.txt,
> c6357-stress-write-latency-99th-1.png
>
>
> Flush writers are a critical element for keeping a node healthy. When several
> compactions run on systems with low performing data directories, IO becomes a
> premium. Once the disk subsystem is saturated, write IO is blocked which will
> cause flush writer threads to backup. Since memtables are large blocks of
> memory in the JVM, too much blocking can cause excessive GC over time
> degrading performance. In the worst case causing an OOM.
> Since compaction is running on the data directories. My proposal is to create
> a separate directory for flushing memtables. Potentially we can use the same
> methodology of keeping the commit log separate and minimize disk contention
> against the critical function of the flushwriter.
--
This message was sent by Atlassian JIRA
(v6.1.5#6160)
