WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] COW in Xen

Marcel Ritter wrote:

Rendon, Curtis schrieb:
Hello,

I had posted this question in Xen-user mailing list three days ago and I did not
get a single answer. On a second thought, maybe xen-devel is more
appropriate so
I am trying again in the hope that I will receive an answer:

Does anybody have an experience (good or bad) with using
COW (Copy-On-Write) storage in Xen ?
I've been using qcow images generated by qemu-img for Linux and
MSWIndows HVM guests, and I've been getting good results. The image
files are much smaller that the equivalently sized raw images.

I simply create them (via gemi-img create -f qcom 10G) and use the
disk=['file:...'] line in my guest configuration files.
If I got Mark right, it's not the image type qcow itself, he's
interested in,
but the COW (Copy-on-write) feature. Some time ago I tried to get
COW working with qcow images, without success. So I guess the name
is missleading, and (in Xen) there's no COW based on qcow.
Not true. CoW functionality is supported in the current blktap driver. If you create a qcow disk on the host using qcow-create with a backing filename argument (can be either a raw image or block device) the driver opens the backing file for reading-only and directs all writes to the qcow child image.

- Julian


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

<Prev in Thread] Current Thread [Next in Thread>