In the last two days I have had two Server 2012 virtual machines on two different Server 2012 Hyper-V host servers pause due to the .vhdx files holding the data drives expanding to fill the host volume that contains the virtual hard disk file.
These are dynamically expanding disks. As a general practice I make the host volume holding the virtual hard disk bigger than the virtual hard disk it is going to contain. In the case of a virtual C: drive I also add space equal to the maximum assigned memory.
In both of the most recent incidents it was a data drive (no memory overhead required) that triggered the crashes. In the case of yesterday's, the VHD had a maximum size of 5.4TB and the container was 5.525TB. In today's crash the container was 55GB larger than the 700GB maximum size of the virtual disk it contained.
My questions are:
1) Is there a rule of thumb or best practice for sizing a host volume or LUN intended to hold a dynamically expanding virtual hard disk?
2) Why do these dynamically expanding virtual hard disk files grow so far beyond the maximum size of the virtual hard disk. Brian, you mention that what is stored in the virtual hard disk makes a difference. Can you elaborate please?
3) Is there a specific point where the container free space becomes too small and the virtual machine crashes? That is to say, is there a threshold free space number, either percent free or MB free, that I can or should be monitoring for so I can catch this before it happens?
These are dynamically expanding disks. As a general practice I make the host volume holding the virtual hard disk bigger than the virtual hard disk it is going to contain. In the case of a virtual C: drive I also add space equal to the maximum assigned memory.
In both of the most recent incidents it was a data drive (no memory overhead required) that triggered the crashes. In the case of yesterday's, the VHD had a maximum size of 5.4TB and the container was 5.525TB. In today's crash the container was 55GB larger than the 700GB maximum size of the virtual disk it contained.
My questions are:
1) Is there a rule of thumb or best practice for sizing a host volume or LUN intended to hold a dynamically expanding virtual hard disk?
2) Why do these dynamically expanding virtual hard disk files grow so far beyond the maximum size of the virtual hard disk. Brian, you mention that what is stored in the virtual hard disk makes a difference. Can you elaborate please?
3) Is there a specific point where the container free space becomes too small and the virtual machine crashes? That is to say, is there a threshold free space number, either percent free or MB free, that I can or should be monitoring for so I can catch this before it happens?