Instance modes are based primarily on whether you have guest tools installed or not: Enhanced mode should be used for instances with guest agent tools installed, and Compatibility mode should be used for instances without guest agent tools installed. If you decide to create your instance from an ISO or a VM you imported to template (e.g. VMDK) it will not have guest tools installed. Guest agent tools are optional, however, they will need to be installed in order to run in enhanced mode. If you would like to know how to perform the installation process and switch to Enhanced mode in Linux click here, and in windows click here.
If you would not like to go through the process of installing guest tools, there are a few things you must know about compatibility mode.
- storage disks are exported as SATA devices instead of SCSI
- vNICs are exported using intel e1000 drivers
- snapshots will be crash-consistent instead of application-consistent
- memory cannot be increased while the instance is running
- Disk Latency graph will not be available (see screenshot below)