Bug 599091

Summary: libvirt: qemu: increase dd block size to speed up domain save
Product: [Community] Virtualization Tools Reporter: Cole Robinson <crobinso>
Component: libvirtAssignee: Laine Stump <laine>
Status: CLOSED CURRENTRELEASE QA Contact:
Severity: medium Docs Contact:
Priority: low    
Version: unspecifiedCC: berrange, crobinso, eblake, laine, xen-maint
Target Milestone: ---   
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Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: libvirt-0.8.2 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
: 601775 (view as bug list) Environment:
Last Closed: 2010-07-21 16:48:55 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 601775    

Description Cole Robinson 2010-06-02 16:38:36 UTC
See https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/524447/comments/5

Apparently increasing the dd block size greatly increases the speed of the domain save operation.

Comment 1 Laine Stump 2010-06-07 17:56:00 UTC
commit 20206a4bc9f1293c69eca79290a55a5fa19976d5 in libvirt git changes the dd blocksize to 1M. This decreased the time required for a save of a suspended 512MB guest from 3min47sec to 56sec.

Comment 2 Eric Blake 2010-06-10 12:19:33 UTC
An additional patch avoids the overhead of seeking to a 1M alignment:
https://www.redhat.com/archives/libvir-list/2010-June/msg00239.html

Comment 3 Daniel Berrangé 2010-07-21 16:48:55 UTC
This is included in 0.8.2. In addition upstream QEMU has identified & fixed a flaw that had significant speed impact