Red Hat Bugzilla – Bug 1234190
[Docs][Admin] For template based VMs, the 'thin' and 'clone' options need to be explained.
Last modified: 2015-09-23 21:41:24 EDT
In the Admin Guide, check the following topics: Exporting a Virtual Machine to the Export Domain Creating a Virtual Machine Based on a Template Creating a Cloned Virtual Machine Based on a Template It currently says a cloned virtual machine is not dependent on the the original template; thinly provisioned templates are dependent on the original template, but it also says when exporting a vm to the export domain, the template for a cloned VM needs to be exported as well for it to work. Question: If a VM is not dependent on a template, why does the template need to be exported as well?
I'll try to do some order, a little long but i try to map all options: user can set the allocation policy in 2 'levels': 1. the way the disk is created - this is the 'storage allocation' level - here 'thin' means the vm disk rely on the template disk, the vm disk is actually a snapshot of the template disk, and the disks are linked together, you cannot delete the template without first deleting the vm. 'clone' means a copy of the template disk, and the 2 disks are not linked, you can delete the template and keep the vm. this is why we say the vm is not dependent on the template. also, copy of the disk takes more time than creating a snapshot. 2. the way the volume is allocated in the storage - this is the 'disk allocation' level (and can be set per disk) - only if user is doing 'clone' (=copy) of the disk from the template (level 1), this creates a new volume, and the user can choose if to use 'thin' or 'preallocated' for the new volumes. here 'thin' creates the volume faster and space is allocated by requirement, 'preallocate' allocate all the requested disk size immediately, this operation is slower. regarding export: vm that is not dependent on it's template, means during create the user chose 'clone' on the storage allocation level (1), can be exported without the template, because it is not linked. and whatever disk allocation (preallocated/thing) doesn't matter. if vm is linked to the template (thin provisioned) - we must have the template on the destination storage domain for this vm to work - OR select 'collapse snapshots' when doing the export - this will collapse the vm disk with the template disk into a single disk and copy it (see above thin means snapshot of the template). if user select 'collapse snapshots' all the snapshots are gone but the vm is not dependent on the template any more and can be exported without it and used on the destination without it.
Thanks for your detailed explanation, Omer. Moving this bug to Docs QA.
Reviewed in cs22765. The topic has been corrected. Minor GUI name fixes made in QA pass. Updated in cs23027 Admin Guide publication spec: Exporting a Virtual Machine to the Export Domain [7515-762929] Revision History [34613-762930] VERIFIED.
Updated flags.