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Bug 741183 - [RFE] Write a tool to align the partition(s) in a Windows XP image to a multiple of 8 sectors
Summary: [RFE] Write a tool to align the partition(s) in a Windows XP image to a multi...
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: libguestfs
Version: 6.3
Hardware: All
OS: Linux
low
medium
Target Milestone: rc
: ---
Assignee: Richard W.M. Jones
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On: 634649 libguestfs_rebase6.3
Blocks: 641489 773650 773651 773677 773696
TreeView+ depends on / blocked
 
Reported: 2011-09-26 07:34 UTC by Richard W.M. Jones
Modified: 2013-01-10 00:23 UTC (History)
14 users (show)

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.
Clone Of: 634649
Environment:
Last Closed: 2012-06-20 06:59:51 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2012:0774 0 normal SHIPPED_LIVE Low: libguestfs security, bug fix, and enhancement update 2012-06-19 19:29:50 UTC

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
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