Bug 584751

Summary: Win7 guests: cannot enable disk caching on IDE disks
Product: Red Hat Enterprise Linux 5 Reporter: Yaniv Kaul <ykaul>
Component: kvmAssignee: chellwig <chellwig>
Status: CLOSED NOTABUG QA Contact: Virtualization Bugs <virt-bugs>
Severity: medium Docs Contact:
Priority: low    
Version: 5.5.zCC: jkt, kwolf, virt-maint, ykaul
Target Milestone: rc   
Target Release: ---   
Hardware: All   
OS: Windows   
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Fixed In Version: Doc Type: Bug Fix
Doc Text:
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Clone Of: Environment:
Last Closed: 2010-05-07 10:41:09 UTC Type: ---
Regression: --- Mount Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Description Yaniv Kaul 2010-04-22 10:49:10 UTC
Description of problem:
Although the option exist (Device Manager -> Disk Drives -> 'QEMU HARDDISJ ATA' -> right click -> Properties -> Policies) to enable write caching, once you check it you get an error that it cannot be set.

On XP/32, you can set this.

Version-Release number of selected component (if applicable):
kvm-83-164.el5_5.6

How reproducible:
Always - both on Win7/32 and Win7/64.

Steps to Reproduce:
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Actual results:


Expected results:


Additional info:

Comment 1 chellwig@redhat.com 2010-04-28 15:40:24 UTC
Note that you never could enabled/disable the write cache under qemu.  While return success for the SETFEATURES calls, we never take any action.  I suspect the difference is that Win7 issues an IDENTIFY call later to check if we actually advertize a cache now.

Note that in recent qemu we will always advertize a write cache,

Comment 2 chellwig@redhat.com 2010-05-07 10:41:09 UTC
Yaniv, is this serious in any way?  Even implementing changing the caching settings is not a high priority, and backporting to RHEL5 certainly isn't.  I'm tempted to close this as WONTFIX.

Comment 3 Yaniv Kaul 2010-05-07 18:51:41 UTC
I don't think it's serious, except for the user experience, where it appears he can do something, then gets a bit of an ugly error. If you don't want to fix it, close as WONTFIX. I guess there are more important bugs to fix.