Bug 861375

Summary: RFE: More info in qemu-img info
Product: [Fedora] Fedora Reporter: Alexander Larsson <alexl>
Component: qemuAssignee: Fedora Virtualization Maintainers <virt-maint>
Status: CLOSED UPSTREAM QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 18CC: amit.shah, berrange, cfergeau, crobinso, dwmw2, itamar, knoel, kwolf, pbonzini, rjones, scottt.tw, stefanha, virt-maint
Target Milestone: ---   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
: 861439 920225 (view as bug list) Environment:
Last Closed: 2012-12-14 20:25:36 EST Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---
Bug Depends On:    
Bug Blocks: 861439, 920225    

Description Alexander Larsson 2012-09-28 08:07:45 EDT
qemu-img info currently give me info like this:

image: /home/alex/.local/share/gnome-boxes/images/Fedora 16
file format: qcow2
virtual size: 11G (11794287616 bytes)
disk size: 4.5G
cluster_size: 65536

In order to figure out the "health" of an image there is some more information I would like:

in-use disk size - I.e the subset of disk size that is not marked as unused due to e.g. TRIM operations

amount of compressed clusters. I.e. "is it useful to re-compress the image".

Fragmentation estimation.

This would be useful to both sysadmins in general and for automated things like
what we want to do in gnome-boxes:
Comment 1 Richard W.M. Jones 2012-09-28 08:18:50 EDT
All sounds useful.  However these requests should probably
go upstream, along with patches!

Note upstream there is a patch floating around which adds
JSON output to qemu-img info.  This is useful because it's
a big security problem to try to parse the text output from
this command.  See:

Comment 2 Daniel Berrange 2012-09-28 11:38:08 EDT
Depending on how Boxes wants to consume this extra metadata, this may need to be done in libvirt instead, or as well. Libvirt does not actually use qemu-img info for getting file metadata, since it wants a low overhead code to extra basic properties & forking qemu-img doesn't really satisfy that.
Comment 3 Paolo Bonzini 2012-09-28 11:39:31 EDT
Fragmentation estimation and in-use space is actually quite expensive to compute---not *that* expensive but certainly worse than a fork, and worse-case O(n) in the size of the disk.
Comment 4 Stefan Hajnoczi 2012-10-23 06:17:08 EDT
Fragmentation statistics have been added to 'qemu-img check' for qcow2 and qed image files:

  commit f8111c241afa75544032dcfa23df0699c91f9866
  Author: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>
  Date:   Thu Mar 15 20:13:31 2012 +0800

      qemu-img: add image fragmentation statistics

Note this is qemu-img check and not qemu-img info, because we need to scan the image metadata (expensive on large images).
Comment 5 Kevin Wolf 2012-10-23 07:58:28 EDT
Yes, I agree that most of this should be part of 'qemu-img check' rather than 'qemu-img info'.

Fragmentation statistics are only implemented for QED as of today, qcow2 doesn't have them yet.
Comment 6 Cole Robinson 2012-12-14 20:25:36 EST
In general I don't think RFE's make much sense in Fedora bugzilla, so I've moved this to the upstream qemu tracker:


Alex, I couldn't find a launchpad account for you, but please follow up on that report (or qemu-devel)