[Bugs] [Bug 1348068] New: High i/ o latency with random write workload from virtual machine(s)

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1348068

            Bug ID: 1348068
           Summary: High i/o latency with random write workload from
                    virtual machine(s)
           Product: GlusterFS
           Version: 3.7.9
         Component: replicate
          Severity: medium
          Priority: medium
          Assignee: bugs at gluster.org
          Reporter: pcuzner at redhat.com
                CC: bugs at gluster.org



Created attachment 1169665
  --> https://bugzilla.redhat.com/attachment.cgi?id=1169665&action=edit
iometer config file

Description of problem:
When using either a replica 3 or sharded replica 3 volume with virtual
machines, profiles that exhibit random writes cause high latencies than can
sometimes span several seconds.

This has been observed with both fio and iometer as load generators

Sequential writes do NOT exhibit this affect

Version-Release number of selected component (if applicable):


How reproducible:
Every time the workload is run this profile is observed


Steps to Reproduce:
1. use either an fio workload with random write or an iometer profile
(attached)
2. track the latency in the vm with pcp
3. 

Actual results:
High latencies are observed which could impact application response times

Expected results:
Spikes in random write workloads are accepted - may be in the 10's of
milliseconds - but latencies that are between 600ms 2s are a problem


Additional info:

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