Bug 741183

Summary: [RFE] Write a tool to align the partition(s) in a Windows XP image to a multiple of 8 sectors
Product: Red Hat Enterprise Linux 6 Reporter: Richard W.M. Jones <rjones>
Component: libguestfsAssignee: Richard W.M. Jones <rjones>
Status: CLOSED ERRATA QA Contact: Virtualization Bugs <virt-bugs>
Severity: medium Docs Contact:
Priority: low    
Version: 6.3CC: abaron, iheim, jzheng, kwolf, leiwang, liko, mbooth, meyering, mkenneth, moli, qwan, rjones, tburke, ykaul
Target Milestone: rcKeywords: FutureFeature, Improvement
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: libguestfs-1.16.2-1.el6 Doc Type: Enhancement
Doc Text:
Cause: Guest has partitions which are not aligned for best performance. Until around 2008, most guests installed themselves non-optimally like this, and this applies even when installing a pre-2008 guest today. Consequence: The guest suffers a performance penalty, as much as 20%. Fix: libguestfs now provides two tools which can diagnose and fix these guests: virt-alignment-scan and (the updated) virt-resize. Result: Customers can use virt-alignment-scan to identify which guests may suffer from poor performance because of unaligned partitions. Furthermore they can fix these guests by using virt-resize. Customers should read the respective manual pages carefully first.
Story Points: ---
Clone Of: 634649 Environment:
Last Closed: 2012-06-20 06:59:51 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: 634649, 719879    
Bug Blocks: 641489, 773650, 773651, 773677, 773696    

Description Richard W.M. Jones 2011-09-26 07:34:52 UTC
+++ This bug was initially created as a clone of Bug #634649 +++

Description of problem:
According to multiple sources (http://media.netapp.com/documents/tr-3747.pdf for example) alignment can have huge impact on performance. Our qcow2 is indeed aligned to 64K boundaries, but then XP goes and install itself on sector 63, which means 31.5K into the first qcow2 cluster. That's not that great.
See the above NetApp PDF, section 4.4.1 and on, how this can easily be fixed pre-installation. libguestfs should do it via its NFS utilities.

This can be later utilized by RHEVM.

--- Additional comment from rjones on 2010-09-17 06:03:33 EDT ---

Mike Snitzer wrote these documents on the issue:

http://people.redhat.com/msnitzer/docs/io-limits.txt
http://people.redhat.com/msnitzer/snitzer_rhsummit_2009.pdf

Comment 2 Richard W.M. Jones 2011-12-06 08:54:44 UTC
If we do the rebase then we will get the two tools
virt-alignment-scan and (updated) virt-resize in RHEL 6.3.

Comment 4 Richard W.M. Jones 2012-02-06 13:23:53 UTC
Setting to modified on the basis that libguestfs 1.16.2 is
available and contains the new tools (virt-alignment-scan
and updated virt-resize).

Comment 7 Richard W.M. Jones 2012-04-26 13:22:02 UTC
    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
Cause:
Guest has partitions which are not aligned for best performance.  Until around 2008, most guests installed themselves non-optimally like this, and this applies even when installing a pre-2008 guest today.

Consequence:
The guest suffers a performance penalty, as much as 20%.

Fix:
libguestfs now provides two tools which can diagnose and fix these guests: virt-alignment-scan and (the updated) virt-resize.

Result:
Customers can use virt-alignment-scan to identify which guests may suffer from poor performance because of unaligned partitions.  Furthermore they can fix these guests by using virt-resize.  Customers should read the respective manual pages carefully first.

Comment 9 Mohua Li 2012-05-14 06:37:56 UTC
set to verified, according to the above result, and i didn't see any side-effect

Comment 14 errata-xmlrpc 2012-06-20 06:59:51 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2012-0774.html