Bug 599091 - libvirt: qemu: increase dd block size to speed up domain save
Summary: libvirt: qemu: increase dd block size to speed up domain save
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Virtualization Tools
Classification: Community
Component: libvirt
Version: unspecified
Hardware: All
OS: Linux
low
medium
Target Milestone: ---
Assignee: Laine Stump
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks: 601775
TreeView+ depends on / blocked
 
Reported: 2010-06-02 16:38 UTC by Cole Robinson
Modified: 2010-07-21 16:48 UTC (History)
5 users (show)

Fixed In Version: libvirt-0.8.2
Doc Type: Bug Fix
Doc Text:
Clone Of:
: 601775 (view as bug list)
Environment:
Last Closed: 2010-07-21 16:48:55 UTC
Embargoed:

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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
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