Bug 518169 – Bad qcow2 performance with cache=off

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Bug 518169 - Bad qcow2 performance with cache=off

Summary:	Bad qcow2 performance with cache=off

Status:	CLOSED ERRATA

Aliases:	None

Product:	Red Hat Enterprise Linux 5
Classification:	Red Hat
Component:	kvm (Show other bugs)
Sub Component:
Version:	5.5
Hardware:	All Linux

Priority	urgent Severity urgent
Target Milestone:	rc
Target Release:	---
Assigned To:	Kevin Wolf
QA Contact:	Lawrence Lim
Docs Contact:

URL:
Whiteboard:
Keywords:	ZStream

Depends On:
Blocks:	520693
	Show dependency tree / graph

Reported:	2009-08-19 05:40 EDT by Kevin Wolf
Modified:	2014-03-25 21:00 EDT (History)
CC List:	7 users (show)

See Also:
Fixed In Version:	kvm-83-113.el5
Doc Type:	Bug Fix
Doc Text:
Story Points:	---
Clone Of:
Environment:
Last Closed:	2010-03-30 03:52:21 EDT
Type:	---
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
windowr2 iometer result. (433.11 KB, application/vnd.oasis.opendocument.spreadsheet) 2010-02-28 20:43 EST, lihuang	no flags	Details
Add an attachment (proposed patch, testcase, etc.)

External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Red Hat Product Errata	RHSA-2010:0271	normal	SHIPPED_LIVE	Important: kvm security, bug fix and enhancement update	2010-03-29 09:19:48 EDT

Groups: None (edit)

Description Kevin Wolf 2009-08-19 05:40:12 EDT

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 06:02:10 EDT

Posted the backports on virtualist.

Comment 5 Lawrence Lim 2009-08-25 11:24:58 EDT

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 07:37:04 EDT

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 2010-02-28 20:43:38 EST

Created attachment 396927 [details]
windowr2 iometer result.

Comment 17 errata-xmlrpc 2010-03-30 03:52:21 EDT

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

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