[Qemu-devel] [PATCH] qemu-img: document qed format on qemu-img man page

[Qemu-devel] [PATCH] qemu-img: document qed format on qemu-img man page

[Stefan Hajnoczi]

The qemu-img.1 man page is missing the qed format from its list of
supported formats.  Document the image creation options for qed.

Suggested-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
When the qcow2 QED mode is merged we can update this again to reflect good
cache=writethrough performance in qcow2v3 /w QED mode.

 qemu-img.texi |   22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/qemu-img.texi b/qemu-img.texi
index 6fc3c28..78640a9 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -232,6 +232,28 @@ to grow.
 
 @end table
 
+@item qed
+Image format with support for backing files and compact image files (when your
+filesystem or transport medium does not support holes).  Good performance due
+to less metadata than the more featureful qcow2 format, especially with
+cache=writethrough.
+
+Supported options:
+@table @code
+@item backing_file
+File name of a base image (see @option{create} subcommand).
+@item backing_fmt
+Image file format of backing file (optional).  Useful if the format cannot be
+autodetected because it has no header, like some vhd/vpc files.
+@item cluster_size
+Changes the cluster size (must be power-of-2 between 4K and 64K). Smaller
+cluster sizes can improve the image file size whereas larger cluster sizes
+generally provide better performance.
+@item table_size
+Changes the number of clusters per L1/L2 table (must be power-of-2 between 1
+and 16).  There is normally no need to change this value but this option can be
+used for performance benchmarking.
+@end table
 
 @item qcow
 Old QEMU image format. Left for compatibility.
-- 
1.7.10

Re: [Qemu-devel] [PATCH] qemu-img: document qed format on qemu-img man page

[Kevin Wolf]

Am 12.06.2012 17:05, schrieb Stefan Hajnoczi:
> The qemu-img.1 man page is missing the qed format from its list of
> supported formats.  Document the image creation options for qed.
> 
> Suggested-by: Michael Tokarev <mjt@tls.msk.ru>
> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> ---
> When the qcow2 QED mode is merged we can update this again to reflect good
> cache=writethrough performance in qcow2v3 /w QED mode.
> 
>  qemu-img.texi |   22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/qemu-img.texi b/qemu-img.texi
> index 6fc3c28..78640a9 100644
> --- a/qemu-img.texi
> +++ b/qemu-img.texi
> @@ -232,6 +232,28 @@ to grow.
>  
>  @end table
>  
> +@item qed
> +Image format with support for backing files and compact image files (when your
> +filesystem or transport medium does not support holes).  Good performance due
> +to less metadata than the more featureful qcow2 format, especially with
> +cache=writethrough.

Can we restrict this clearly to cache=writethrough only and possibly add
a few words about QED's future?

It's good to have the option today for the few people that actually need
cache=writethrough, but I don't want more people than necessary to use
it only to notice after a while that there's no more active development
of QED and they have to do a painful conversion of all their images.

Kevin

Re: [Qemu-devel] [PATCH] qemu-img: document qed format on qemu-img man page

[Stefan Hajnoczi]

On Tue, Jun 12, 2012 at 05:15:29PM +0200, Kevin Wolf wrote:
> Am 12.06.2012 17:05, schrieb Stefan Hajnoczi:
> > The qemu-img.1 man page is missing the qed format from its list of
> > supported formats.  Document the image creation options for qed.
> > 
> > Suggested-by: Michael Tokarev <mjt@tls.msk.ru>
> > Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> > ---
> > When the qcow2 QED mode is merged we can update this again to reflect good
> > cache=writethrough performance in qcow2v3 /w QED mode.
> > 
> >  qemu-img.texi |   22 ++++++++++++++++++++++
> >  1 file changed, 22 insertions(+)
> > 
> > diff --git a/qemu-img.texi b/qemu-img.texi
> > index 6fc3c28..78640a9 100644
> > --- a/qemu-img.texi
> > +++ b/qemu-img.texi
> > @@ -232,6 +232,28 @@ to grow.
> >  
> >  @end table
> >  
> > +@item qed
> > +Image format with support for backing files and compact image files (when your
> > +filesystem or transport medium does not support holes).  Good performance due
> > +to less metadata than the more featureful qcow2 format, especially with
> > +cache=writethrough.
> 
> Can we restrict this clearly to cache=writethrough only and possibly add
> a few words about QED's future?
> 
> It's good to have the option today for the few people that actually need
> cache=writethrough, but I don't want more people than necessary to use
> it only to notice after a while that there's no more active development
> of QED and they have to do a painful conversion of all their images.

Yes, that makes sense.  Will send a v2.

Stefan