Re: [Engine-devel] [vdsm] RFC: Writeup on VDSM-libstoragemgmt integration

On 06/25/2012 08:28 PM, Ryan Harper wrote: >* Andrew Cathrow<acathrow(a)redhat.com> [2012-06-24 21:11]: >> >>----- Original Message ----- >>>From: "Andy Grover"<agrover(a)redhat.com> >>>To: "Shu Ming"<shuming(a)linux.vnet.ibm.com> >>>Cc: libstoragemgmt-devel(a)lists.sourceforge.net, engine-devel(a)ovirt.org, "VDSM Project Development" >>><vdsm-devel(a)lists.fedorahosted.org> >>>Sent: Sunday, June 24, 2012 10:05:45 PM >>>Subject: Re: [vdsm] [Engine-devel] RFC: Writeup on VDSM-libstoragemgmt integration >>> >>>On 06/24/2012 07:28 AM, Shu Ming wrote: >>>>On 2012-6-23 20:40, Itamar Heim wrote: >>>>>On 06/23/2012 03:09 AM, Andy Grover wrote: >>>>>>On 06/22/2012 04:46 PM, Itamar Heim wrote: >>>>>>>On 06/23/2012 02:31 AM, Andy Grover wrote: >>>>>>>>On 06/18/2012 01:15 PM, Saggi Mizrahi wrote: >>>>>>>>>Also, there is no mention on credentials in any part of the >>>>>>>>>process. >>>>>>>>>How does VDSM or the host get access to actually modify the >>>>>>>>>storage >>>>>>>>>array? Who holds the creds for that and how? How does the user >>>>>>>>>set >>>>>>>>>this up? >>>>>>>>It seems to me more natural to have the oVirt-engine use >>>>>>>>libstoragemgmt >>>>>>>>directly to allocate and export a volume on the storage array, >>>>>>>>and >>>>>>>>then >>>>>>>>pass this info to the vdsm on the node creating the vm. This >>>>>>>>answers >>>>>>>>Saggi's question about creds -- vdsm never needs array >>>>>>>>modification >>>>>>>>creds, it only gets handed the params needed to connect and use >>>>>>>>the >>>>>>>>new >>>>>>>>block device (ip, iqn, chap, lun). >>>>>>>> >>>>>>>>Is this usage model made difficult or impossible by the current >>>>>>>>software >>>>>>>>architecture? >>>>>>>what about live snapshots? >>>>>>I'm not a virt guy, so extreme handwaving: >>>>>> >>>>>>vm X uses luns 1& 2 >>>>>> >>>>>>engine -> vdsm "pause vm X" >>>>>that's pausing the VM. live snapshot isn't supposed to do so. >>>>Tough we don't expect to do a pausing operation to the VM when live >>>>snaphot is undergoing, the VM should be blocked on the access to >>>>specific luns for a while. The blocking time should be very short >>>>to >>>>avoid the storage IO time out in the VM. >>>OK my mistake, we don't pause the VM during live snapshot, we block >>>on >>>access to the luns while snapshotting. Does this keep live snapshots >>>working and mean ovirt-engine can use libsm to config the storage >>>array >>>instead of vdsm? >>> >>>Because that was really my main question, should we be talking about >>>engine-libstoragemgmt integration rather than vdsm-libstoragemgmt >>>integration. >>for snapshotting wouldn't we want VDSM to handle the coordination of >>the various atomic functions? >Absolutely. Requiring every management application (engine, etc) to >integrate with libstoragemanagement is a win here. We want to simplify >working with KVM, storage, etc not require every mgmt application to >know deep details about how to create a live VM snapshot. > Sorry, but not clear to me. Are you saying engine-libstoragemgmt integration is a win here ?

VDSM is the common factor here.. so integrating libstoragemgmt with VDSM helps anybody talkign with VDSM in future AFAIU.