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https://issues.apache.org/jira/browse/CASSANDRA-7567?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14078786#comment-14078786
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Ryan McGuire edited comment on CASSANDRA-7567 at 7/30/14 2:10 AM:
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Sorry for the confusion, I don't think I tested this on 2.0 after all. Just
now, I was unable to see the same latency spikes on 2.0.8 nor 2.0 HEAD. I do
seem them on 2.1 HEAD and I'm preparing logs and traces for that run.
was (Author: enigmacurry):
Sorry for the confusion, I don't think I tested this on 2.0 after all, I was
unable to see the same latency spikes on 2.0.8 nor 2.0 HEAD. I do seem them on
2.1 HEAD and I'm preparing logs and traces for that run.
> when the commit_log disk for a single node is overwhelmed the entire cluster
> slows down
> ---------------------------------------------------------------------------------------
>
> Key: CASSANDRA-7567
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7567
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Environment: debian 7.5, bare metal, 14 nodes, 64CPUs, 64GB RAM,
> commit_log disk sata, data disk SSD, vnodes, leveled compaction strategy
> Reporter: David O'Dell
> Assignee: Brandon Williams
> Attachments: 7567.logs.bz2, write_request_latency.png
>
>
> We've run into a situation where a single node out of 14 is experiencing high
> disk io. This can happen when a node is being decommissioned or after it
> joins the ring and runs into the bug cassandra-6621.
> When this occurs the write latency for the entire cluster spikes.
> From 0.3ms to 170ms.
> To simulate this simply run dd on the commit_log disk (dd if=/dev/zero
> of=/tmp/foo bs=1024) and you will see that instantly all nodes in the cluster
> have slowed down.
> BTW overwhelming the data disk does not have this same effect.
> Also I've tried this where the overwhelmed node isn't being connected
> directly from the client and it still has the same effect.
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