Bug 518169

Summary: Bad qcow2 performance with cache=off
Product: Red Hat Enterprise Linux 5 Reporter: Kevin Wolf <kwolf>
Component: kvmAssignee: Kevin Wolf <kwolf>
Status: CLOSED ERRATA QA Contact: Lawrence Lim <llim>
Severity: urgent Docs Contact:
Priority: urgent    
Version: 5.5CC: ehabkost, lihuang, riek, tburke, tools-bugs, virt-maint, ykaul
Target Milestone: rcKeywords: ZStream
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: kvm-83-113.el5 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2010-03-30 07:52:21 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 520693    
Attachments:
Description Flags
windowr2 iometer result. none

Description Kevin Wolf 2009-08-19 09:40:12 UTC 
We had to change the default options for qcow2 to cache=off to avoid data corruption on host crashes. After this change, there have been reports that installations took 2 hours which previously had taken 15 minutes. Upstream qemu has performance fixes that should help here. They need to be backported to RHEL.
Comment 1 Kevin Wolf 2009-08-19 10:02:10 UTC 
Posted the backports on virtualist.
Comment 5 Lawrence Lim 2009-08-25 15:24:58 UTC 
Hi Kevin,
Could you please provide us with a scratch build which we could test and compare against the current implementation?

Thanks,
Lawrence
Comment 8 Kevin Wolf 2009-08-28 11:37:04 UTC 
Hi Lawrence,

I have just created https://brewweb.devel.redhat.com/taskinfo?taskID=1948061. I'm doing this for the first time, so while I hope this is what you need, I'm not 100% sure about it. If it isn't quite right just let me know and I'll make another attempt at it.
Comment 14 lihuang 2010-03-01 01:43:38 UTC 
Created attachment 396927 [details]
windowr2 iometer result.
Comment 17 errata-xmlrpc 2010-03-30 07:52:21 UTC 
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2010-0271.html