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[Bug 1634161] Re: Default multipath policy is round-robin, shows considerably worse read throughput compared to using service-time

To: group.of.nepali.translators@xxxxxxxxxxxxxxxxxxx
From: Launchpad Bug Tracker <1634161@xxxxxxxxxxxxxxxxxx>
Date: Sat, 18 Mar 2017 07:29:43 -0000
Reply-to: Bug 1634161 <1634161@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx

This bug was fixed in the package multipath-tools - 0.6.4-3ubuntu2

---------------
multipath-tools (0.6.4-3ubuntu2) zesty; urgency=medium

  * debian/initramfs/hooks:
    - Remove old dm-emc module; it hasn't been in kernel since 2.6.27.
    - Add dm-queue-length: users may want to change from the default selector
      and should be able to do so. (LP: #1673350)
  * debian/patches/path_selector.patch, debian/patches/series: remove
    path_selector.patch to get back to the "right" default selector of
    service-time, which has been included in the kernel module packages for
    a while now and has better throughput than round-robin. It's also the
    default upstream. (LP: #1634161)

 -- Mathieu Trudel-Lapierre <cyphermox@xxxxxxxxxx>  Fri, 17 Mar 2017
09:37:36 -0400

** Changed in: multipath-tools (Ubuntu)
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1634161

Title:
  Default multipath policy is round-robin, shows considerably worse read
  throughput compared to using service-time

Status in Ubuntu on IBM z Systems:
  In Progress
Status in multipath-tools package in Ubuntu:
  Fix Released
Status in multipath-tools source package in Xenial:
  New

Bug description:
  ---Problem Description---
  Default multipath policy is round-robin, shows considerably worse read throughput compared to using service-time
  Contact Information = Barbara Mundle, barbara.mundle@xxxxxxxxxx 
  ---uname output---
  4.4.0-21-generic
  Machine Type = z systems: Type 2964, Model 701 NC9 
  ---Debugger---
  A debugger is not configured
  ---Steps to Reproduce---
   Conducting throughput measurements with both policies shows the difference

  Userspace tool common name: multipath-tools 
  The userspace tool has the following bit modes: 64-bit 
  Userspace rpm: multipath-tools_0.5.0+git1.656f8865-5ubuntu2.2_s390x.deb 
  Userspace tool obtained from project website:  na 
   
  *Additional Instructions for Barbara Mundle, barbara.mundle@xxxxxxxxxx:
  -Attach ltrace and strace of userspace application.

  Throughput numbers with FIO for sequential read (in KBPS) with
  multipath policies service.time/round-robin (varying with number of
  jobs from 1 - 64):

            service-time   round-robin

  1        3193030         2917220 
  2        5248430         5020375
  4        8453570         6438140
  8        9708690         6444175
  16      9712100         6448080
  32      9714035         6450905
  64      9718355         6461650

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