Am 25.05.2017 um 20:44 hat Bruno Alvisio geschrieben: > Hello John, > > Thanks. Yes, typo when I wrote the e-mail. > > It might be possible that XEN does that (I will ask in the XEN forum). > However, > I have noticed that it is not the case for all of the VMs I have launched. In > some of them I can query the block devices even after a long time the VM has > been running. > > I was wondering if the device is removed in case the disk is corrupted or > something. When I mention it runs normally, I can log into ithe VM and perform > read/write operations such creating files. > > Also, is there an easy way to log all qemu events so that I can see what might > be going on with the 'ide' device?
There is one completely crazy thing that Xen does with respect to disks. Instead of having support for their PV disks (i.e. virtio-blk, just different) in the BIOS, they add _both_ an IDE disk and a PV disk to the VM, so that the bootloader or non-PV-aware guest OSes can access the IDE disk, for which they most certainly do have drivers. As soon as a driver for the PV disk is loaded, however, that driver calls a hypervisor function that removes all the IDE disks from the VM and leaves only the PV ones there, so that the PV-aware guest doesn't see two same disks. I suspect that what you're seeing initially is the IDE disks, and when the PV driver is loaded, they disappear. Kevin
