Is there something that when the VM has snapshot then it pointing to delta disk rather than flat-vmdk?
Yes,
when you take a snapshot, a delta vmdk is created. All changes on the filesystem will be changed inside this vmdk.
Here's a nice read: VMware KB: Understanding virtual machine snapshots in VMware ESXi and ESX
Tim
Yes, that's how snapshots work. The flat as well as the delta files are use like a chain, and the VM will point to the latest chain link (snapshot file). You can see this in either the VM's HDD properties in the GUI, or in the VM's configuration (.vmx) file.
André
Yes. Absolutely. The base flat-vmdk will be set as a Read-Only Disk and the new snapshot delta disk will be created on top of that. All the R/Ws will go to the new snapshot delta disk. If old data is required, it would read it from the Read-Only mounted base disk. Incase if the old data has to be modified which is there on the base disk, the modified data will be written to the snapshot delta disk without changing the base disk when its running on the snapshot. This is how the state of the VM with the base disk will be preserved when running on the snapshot.
