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Ryan McGuire edited comment on CASSANDRA-7567 at 7/30/14 2:10 AM: ------------------------------------------------------------------ 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. -- This message was sent by Atlassian JIRA (v6.2#6252)