----- Original Message ----- > From: "Osier Yang" <jyang@xxxxxxxxxx> > To: libvir-list@xxxxxxxxxx > Cc: "Daniel Erez" <derez@xxxxxxxxxx> > Sent: Tuesday, November 26, 2013 12:24:02 PM > Subject: Re: VirtIO-SCSI disks limitation > > [[ TO libvir-list ]] > > Hi, Daniel, > > I'm going to share the thread to public list for further discussion. > Hope you > don't mind. > > On 26/11/13 02:37, Daniel Erez wrote: > > Hi Osier, > > > > It seems there's a limitation in libvirt that allows up to six disks in a > > virtio-scsi controller. I.e. when sending more than six disks, libvirt > > automatically creates a new controller but of type virtual LSI Logic SCSI. > > Is this behavior a known issue? > > For narrow SCSI bus, we allow 6 disks indeed. > > For wide SCSI bus, we allow 15 disks (not including the controller > itself on unit 7). > > I'm doubting if we have problem on detecting if it supports wide SCSI > bus though, since as far as I see from the user cases, it's always > narrow SCSI bus. > > > Shouldn't libvirt allow up to 256 disks > > per controller or at least create a new controller of type virtio-scsi when > > needed? > > The controller model for virtio-scsi controller is lsilogic, which we can't > change simply, since it might affect the existing guests. > > There was the similar discussion in libvir-list before [1]. > > But auto generation for controller is quite old, which I'm also not quite > clear about. I'd like see another discussion to make it more clear whether > we should do some work for upper layer app (e.g. oVirt). > > Basicly two points: > > * Should we do some changes on the maximum units for a SCSI controller, > I.e. Should 7 (narrow bus) 16 (wide bus) be changed to other numbers? > I'm afraid the changes could affect existing guests though. > > * Do we really want to put the burden on users, I.E, let them create the > controller explicitly. For use cases like one wants to add many > disks for > a guest, they need to know whether it's narrow SCSI bus or wide SCSI > bus first (which we don't expose outside), and then do the calculation > to know when to create a new SCSI controller. > > @Daniel, am I correct on your problems? Please comments if it doesn't > cover all your thoughts. So, IIUC, we can't reach the limitation of 256 disks per controller? I.e. we must explicitly ask for a new controller every 6/15 disks? BTW, how do I define in the XML the bus type (narrow/wide)? > > [1] http://www.redhat.com/archives/libvir-list/2012-November/msg00537.html > > Regards, > Osier > > > > > [the issue as been discussed as part of: http://gerrit.ovirt.org/#/c/20630] > > > > Thanks, > > Daniel > > > > > > ----- Original Message ----- > >> From: "Dave Allan" <dallan@xxxxxxxxxx> > >> To: "Daniel Erez" <derez@xxxxxxxxxx> > >> Cc: "Ayal Baron" <abaron@xxxxxxxxxx>, "Osier Yang" <jyang@xxxxxxxxxx>, > >> "John Ferlan" <jferlan@xxxxxxxxxx> > >> Sent: Monday, November 25, 2013 8:19:42 PM > >> Subject: Re: VirtIO-SCSI disks limitation > >> > >> Hi Daniel, > >> > >> Talk to Osier Yang and John Ferlan (cc'd). > >> > >> Dave > >> > >> > >> On Mon, Nov 25, 2013 at 12:48:45PM -0500, Daniel Erez wrote: > >>> Hi Dave, > >>> > >>> I'm an engineer at oVirt team and I'm working on VirtIO-SCSI integration. > >>> I would appreciate it if you could refer me to a point of contact at > >>> libvirt. > >>> In specific, I need to know if there's any hardcoded limitation for the > >>> number of disks per VirtIO-SCSI controller. > >>> > >>> Best Regards, > >>> Daniel > > -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list