Qcow2 converted to vmdk show as spare and can’t be snapshot

You have to pay for vSphere with its various modules and extra features but not to use the vSphere Client to connect to a free ESXi.

I think where you may be getting the license message from is although ESXi is free, you still need to request a free license key from VMWare.

Login to your ESXi box with vSphere Client and go to Configuration -> Licensed Features -> Edit.

If you are set to evaluation mode, that is what you are getting the license warning from.

VMWare should have emailed you a license key when you signed up on their website to download ESXi. If not, you can go through the download steps again and the license key should be on one of the pages.

For me, if I go to https://www.vmware.com/products/esxi/ hit Download, login with my free VMWare account, then on the page with all of the download links, at the top of the list is my ESXi License.

The reason you are seeing the license message about vSphere is that in the Evaluation mode, some of the extra features that are only available with vSphere are enabled, once you enter a free ESXi license, those will be disabled and you won't get prompted anymore.

Also, you can use the vCenter Converter in the standalone mode (runs off of your workstation) for free with ESXi. This tool is immensely useful for moving VMs on and off of ESXi. http://www.vmware.com/products/converter/.

When a VM has an active snapshot, its virtual disk I/O is not performed on the VM's actual .VMDK files, but instead they are kept unchanged, and whatever changes in the VM is written to different physical files; this allows for the recovery of the previous VM state, but has three important side effects:

• Disk I/O for the VM is much slower.
• Those "delta" files keep growing over time, as more and more disk I/O is performed by the VM.
• When the snapshot is removed, the changes stored in the "delta" files have to be merged back into the main .VMDK files, and this is is very slow and time consuming if the snapshot has been active for a long time.

It is indeed better to not keep active snapshots for a long time. If you need a long-term backup of a VM in a given state, you can just copy the VM somewhere else: this will have no performance impact on the VM, and you'll anyway end up using less disk space than what long-term snapshots would fill up over time.

Also, having a copy of the VM stored in a different place will actually help you if you lose the VM: snapshots are stored together with the VM they belong to, and are only useful if the VM is available; they are totally useless in the case of an actual data loss (like a datastore crash), and thus can't be used as real backups.

Here is some official documentation about snapshots:

http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&externalId=1015180