I am trying to understand how checkpoints affect disk space for a virtual machine that is stored on our SAN. For example, we have a virtual machine that has (2) hard drives attached to it, both located on our SAN. It is my understanding that if I create a checkpoint (snapshot) of this machine, the existing .vhd files will essentially stop growing and two .avhd files will be created to continue growing in size with everything new that takes place from the time the checkpoint is taken. We have a mixture of dynamic disks and fixed disks in our virtual environment and my question is if on our EVA SAN we dedicate 80 GB to a particular hard drive and then when we create a virtual machine and point to that location on the SAN and tell the drive to be 70 GB in size and it is fixed, will the new .avhd file also use that dedicated 70 GB of space or will it create a file on the SAN, in the same location as the existing .vhd and only have the remaining 10 GB of space left to work with, which is reserved for memory and thus cause the virtual machine to crash because it is out of space? If using a fixed disk, do we need to allow more room on the SAN for that new file to grow or can it just utilize the existing space defined when creating the virtual machine in Virtual Machine Manager. I just know that typically when you have a fixed disk scenario and you look at the host it appears like it is full because the full 70 GB shows up as used, even though on the virtual machine itself it really is not used.
That leads to the second question, in a dynamic situation, if you say you want a 70 GB hard drive, it grows as it needs space, who does the checkpoint work there, does it use the same 70 GB you dedicated when building the machine or does it go to the SAN and start growing, thus taking away space from the 70 GB you dedicated, thus causing premature space issues?