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Re: [Xen-devel] A Problem with Page Cache in Xen

In the situation I consider here,the VM C won't be running again after it's set up.The existence of VM C is  only for VM A and VM B's running.If VM A or VM B change some blocks in its file system,the change will only be stored in its own virtual disk image whose format is QCOW2.That's meaning which I would like to express.However I cannot find the solution to my problem temporarily.Your further suggest is helpful for me.

At 2012-01-31 00:18:58,"Ian Campbell" <Ian.Campbell@xxxxxxxxxx> wrote: >On Mon, 2012-01-30 at 08:11 +0000, hxkhust wrote: >> Hi, >>   >> Recently I'm dong some reserch on xen and encounter a problem that I >> cannot solve temporarily.I need your help very much and the following >> is the question I would like to ask: >> On a physical machine with xen virtualization platform installed ,VM >> A,VM B are VM C's virtual disks are all image files,among which VM A >> and VM B's virtual disks are QCOW2 format and VM C's disk is RAW >> format. And VM A and VM B's virtual disk image files are based on VM >> C's virtual disk image file.Now these three VMs are running on the >> same physical machine with xen installed. > >This is an invalid/dangerous configuration. You can't really safely >write to the backing file (C's raw disk) while there are active users (A >and B's qcow2 images) of it. Imagine e.g. that all three change the same >bit of filesystem metadata in different ways... > >Ian. > >

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