Re: [Kimchi-devel] Rethink the Relationship of Template and VM

On 04/28/2014 01:45 PM, Mark Wu wrote: > On 04/27/2014 10:38 PM, Zhou Zheng Sheng wrote: >> Hi all, >> >> I'm working on host device passthrough. A a problem troubles me: I see >> in current Kimchi code, when adding a specific SCSI or iSCSI LUN, it is >> added to the template but not the VM. This is counter-intuitive, because >> a template is to store the common information for lots of VMs, while a >> specific LUN should only be used by just one VM. It's OK for DIR, NFS >> and Logical storage pool being managed by the template, because actually >> the template allocates a new specific volume for a new VM, so the >> specific volume goes with the specific VM but not the template. Since we >> don't define a specific DIR storage volume in the template, why we >> define a concrete LUN in it? >> >> The first problem in the current design is that we can not attach a new >> LUN to a VM after the VM is created. >> >> Another problem is that we mix the "things in common" and "things >> special" in template, thus we make its responsibility complex. Static >> and dynamic validations are also mixed in template. >> >> The third problem is that if we get 10 LUNs for 10 VMs, the user has to >> create 10 templates at first, then create 10 VMs from the 10 templates >> respectively. It's a bit tedious. >> >> The fourth problem is that if a LUN is used by a VM, usually it should >> not be used by other VMs, so it implies that by specifying a LUN in a >> template, the template should only create just one VM. What's the point >> to make a template that only produces one VM? >> >> It seems a cleaner way is putting SCSI LUN handling code in VM. Firstly, >> we can assign a SCSI/iSCSI storage pool to the template. When it's time >> to create a VM from the template, Kimchi lists all the available LUNs in >> the storage pool and the user can just pick some LUNs. The VM override >> parameters are suitable to store the LUNs information. It also makes >> possible to implement some mechanisms to add/remove LUNs after a VM is >> created, which is a very typical user requirement. >> >> The same problem exists in host device passthrough. For a specific >> device, it should be passthrough to a specific VM but not a template >> I'd like to collect some thoughts before my device passthrough patch V2. >> In which place you'd suggest me to put device passthrough information, >> template or VM? > Template should NOT include any vm specific information. As I mentioned > in the comments of your pci passthrough patch, we need allow user have > chance to customize the configuration when creating vm based on > template. ACK