Il 23/07/2013 16:14, Daniel P. Berrange ha scritto: > On Tue, Jul 23, 2013 at 03:52:56PM +0200, Paolo Bonzini wrote: >> Il 23/07/2013 15:36, Daniel P. Berrange ha scritto: >>> On Tue, Jul 23, 2013 at 03:29:40PM +0200, Paolo Bonzini wrote: >>>> Il 23/07/2013 15:26, Daniel P. Berrange ha scritto: >>>>>>> >>>>>>> Ok, this answers my question. :) >>>>>>> >>>>>>> I think the default mode should be direct, because otherwise things such >>>>>>> as persistent reservations do not work. >>>>> No, the default has to be host mode, because that is the only mode that >>>>> is guaranteed to be usable with any QEMU. The direct mode requires a >>>>> QEMU that is new enough, and a distro to have enabled it. We can't >>>>> rely on that as a default choice. >>>> >>>> Volume sources are also new enough that you can assume a good QEMU. >>> >>> No we can't assume that. New libvirt is frequently used with old QEMU >>> and we want to have good default behaviour there. >> >> New libvirt, yes. But can't new libvirt features also assume a new QEMU >> if the old one causes more trouble than anything? > > I've no problem with new features requiring new QEMU but that's not > the issue here. This is a question about what the default configuration > should be. For default configuration we aim for maximum compatibility > not the latest possible features. Shouldn't default configuration be simply "what makes the most sense"? >> If you use host mode and the guest issues reservation commands, you may >> get data corruption. That is the brokenness. > > So be it, that's been the case for every version of libvirt and QEMU > in existance up until iscsi protocol support was added, so it is not > a new issue. That doesn't justify choosing a default that is guaranteed > to not work at all. I started adding iSCSI support to ensure that iSCSI LUNs would work. This makes them _not_ work by default. It makes me regret asking to add support for volumes as a disk source. Paolo -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list