<div dir="ltr"><div><div><div><div>Hi,<br><br></div>NFS will be sparse. Preallocate is relevant for block storage.<br><br></div>There is a fix to change the UI to display the format (RAW/QCOW2) of the disk instead of the type (Sparse/Preallocated) [1].<br>When creating a VM from a template, If you choose thin provisioning the disk format will be alway QCOW2, keeping the disk from the template as is read-only and creating a disk only for the diffs.<br></div>If you choose Clone, then the whole disk will be copied and you will have a new copy of template disk in whatever format you want (Raw or QCOW2).<br><br>>What happens if you clone a source VM which is using "thin" ?<br></div>The VM cloned from a thin templated base VM will be created with a full copy of the disk (as in "Clone" when creating from template)<br><br><div><div>>Interesting. Is there a way to "merge" the changes ? (I mean to change it from being "thin provision" after its creation and make it an independent VM)<br>No, a VM created as thin will remain like that. You can clone a new VM from it and them you will have an "independent VM"<br><br>>When you create a template for the first time, it seems you can't choose between clone and thin, which one is used ?<br></div><div>When you create a template you make a read-only copy of the VM disks (Clone) . You can choose the format of the disks (RAW/QCOW2)<br></div><div><br>[1] <a href="https://gerrit.ovirt.org/#/c/57190/" target="_blank">https://gerrit.ovirt.org/#/c/57190/</a><br></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, May 23, 2016 at 3:50 PM, Alexis HAUSER <span dir="ltr"><<a href="mailto:alexis.hauser@telecom-bretagne.eu" target="_blank">alexis.hauser@telecom-bretagne.eu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">>Regarding your examples, I cannot say exactly because of lack of some<br>
>details. What storage type are you using? How do you measure the space used<br>
>on the physical disk?<br>
<br>
<br>
</span>simply df -h on the PC sharing the NFS storage.<br>
<span class=""><br>
<br>
>> For example, when making a VM from template, using pre-allocated disk<br>
>> option, for a 50GB Virtual disk, it only uses 3GB on the physical disk.<br>
<br>
> 3GB is the VM's disk? What about the disk of the template?<br>
<br>
<br>
</span>3GB is the difference using df -h betweem before making the template, and after making it and running the VM.<br>
<span class=""><br>
<br>
>Generally, 50GB pre-allocated disk will take 50GB of physical space. A 50GB<br>
>sparse disk will take as many 1GB chunks as needed to store all the<br>
>information that was written to it, maximum 50GB.<br>
<br>
<br>
</span>so "pre-allocated" doesn't use pre-allocation but sparse instead ? I don't really get it, sorry.<br>
<span class=""><br>
<br>
>When you create a VM by cloning another VM or create a VM from a template<br>
>in "clone" mode, a copy of the source disk will be created. The new disk<br>
>will take as much space as the source disk did.<br>
<br>
<br>
</span>What happens if you clone a source VM which is using "thin" ?<br>
<span class=""><br>
<br>
>When you create a VM from a template in "thin provision" mode or creating a<br>
>VM in a pool, the new disk will be initially only a reference to the source<br>
>disk. Reading from it will read the source disk. Writing to it will write<br>
>to the new disk, not touching the source. Thus, all disk fragments that<br>
>were overwritten after disk creation will be physically stored in the new<br>
>disk and read from it, those that were not overwritten, will be read from<br>
>the source disk.<br>
<br>
<br>
</span>Interesting. Is there a way to "merge" the changes ? (I mean to change it from being "thin provision" after its creation and make it an independent VM)<br>
When you create a template for the first time, it seems you can't choose between clone and thin, which one is used ?<br>
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