Re: [Engine-devel] Question about CloneVMFromSnapshot feature in context of shared disks and direct LUNs-based disks

From: "Ayal Baron" <abaron(a)redhat.com&gt; To: "Miki Kenneth" <mkenneth(a)redhat.com&gt; Cc: engine-devel(a)ovirt.org, "Itamar Heim" <iheim(a)redhat.com&gt; Sent: Friday, January 20, 2012 1:37:54 PM Subject: Re: [Engine-devel] Question about CloneVMFromSnapshot feature in context of shared disks and direct LUNs-based disks ----- Original Message ----- > Sorry guys if I was not clear or maybe I missed something... > > Let's take a use case: > - User like to create a VM for instance Win 2008, and would like to > attach a shared disk to it. > - User liked to create multiple copies of this VM. > (all vms shared the same disk, and run same OS). > so do I do that in oVirt.... we can do either option 2 or 3. > > Option 2 as I read it: > Taking the snapshot and marking the shared disk and direct LUN > disks as unplugged (in the VM snapshot configuration) and marking > the > snapshot state as partial. > > my understanding was: > 1. we is clone the vm configuration as is. > 2. we try to clone the different disks > 3. if there is shared raw disk/direct LUN, we do not clone them, we > "unplug" them. > 4. the (poor) user, will have to plug these vms manually, in order > to > assure connectivity and raise awareness that these disks are > "special". This is nice but not great. Correct > > Option 3 as I read it: > Taking the snapshot and marking the shared disk and direct LUN > disks as plugged (in the VM snapshot configuration) and marking > these > disks as read only. > > my understanding was: > 1. we is clone the vm configuration as is. > 2. we try to clone the different disks > 3. if there is shared raw disk/direct LUN, we do not clone them , > we > make them read only(?), and they remain plugged. > 4. user is happy. > 5. only issue is how we have to make the user aware that these > disks > are shared/read only??? > if this is possible, I agree to vote for third option :) This will become apparent to the user once he boots the machine and gets the kernel panic :)

> > You might want to have a look at: > http://www.symantec.com/connect/articles/building-vmware-shared-disk > (look at the configuration file in Vmware: > disk.locking = "FALSE" > diskLib.dataCacheMaxSize = "0" > #scsi1 data storage > scsi1.present = "TRUE" > scsi1.virtualDev = "lsilogic" > scsi1.sharedbus = "none" > scsi1:0.present = "TRUE" > scsi1:0.fileName = " D:\Virtual Machines\Shared > Disk\SHARED-DISK.vmdk > " > scsi1:0.mode = "independent-persistent" > scsi1:0.shared = "TRUE" > scsi1:0.redo = "" > The shared flag is set for shared file, indicating "no locking" This is shared disk, what about RDM?

> > I would like to re-ephasize that the user does not know the > snapshotting mechanics. He would like to "copy" the VM as is. We > have to do our best, and highlights the issues/sensitive points he > has to take care of. > > > does that make sense? > > Miki > > > > ----- Original Message ----- > > From: "Itamar Heim" <iheim(a)redhat.com&gt; > > To: "Livnat Peer" <lpeer(a)redhat.com&gt; > > Cc: engine-devel(a)ovirt.org > > Sent: Friday, January 20, 2012 7:21:34 AM > > Subject: Re: [Engine-devel] Question about CloneVMFromSnapshot > > feature in context of shared disks and direct > > LUNs-based disks > > > > On 01/20/2012 12:01 PM, Livnat Peer wrote: > > > On 20/01/12 09:35, Ayal Baron wrote: > > >> > > >> > > >> ----- Original Message ----- > > >>> Top Posting: > > >>> > > >>> From user POV I think that option 2 is the only one that > > >>> make > > >>> sense. > > >>> We try to do as much as we can, > > >>> and on each "problematic" case, we make him aware and let him > > >>> decide. > > >>> > > >> > > >> Yep, +1. > > >> > > > > > > Trying to get to a conclusion here, > > > 3 different people said on this thread that they think that > > > from > > > the > > > user perspective leaving the shared devices plugged is what > > > they > > > think > > > is the best behavior to the user. (Omer, Kolesnik, Yair) > > > > > > On the other hand we have 2 people who think that protecting > > > the > > > user is > > > more important than leaving the VM configuration as it was in > > > the > > > original VM (Miki, Ayal). > > > > > > Ayal/Miki can you please specify what are we protecting the > > > user > > > from? > > > > > > > > > I think that because we are not snapshotting the shared disk > > > and > > > the > > > direct LUN they should not be part of the VM configuration (in > > > the > > > snapshot) at all. we can not promise the user that the disk > > > will > > > be > > > there and if it is there we can not guarantee it is in the same > > > state as > > > it was when we took the snapshot. > > > > > > > > > Another issue, > > > > > > I can not see a reason to limit this feature to creating a VM > > > from > > > snapshot and not a template? Almost no extra work is needed for > > > supporting templates as well. > > > > I assume you meant, creating a VM from another VM (if it is > > down)? > > It should be supported. > > _______________________________________________ > > Engine-devel mailing list > > Engine-devel(a)ovirt.org > > http://lists.ovirt.org/mailman/listinfo/engine-devel > > > _______________________________________________ > Engine-devel mailing list > Engine-devel(a)ovirt.org > http://lists.ovirt.org/mailman/listinfo/engine-devel >