The following is an excerpt from my “What’s New in VMware vSphere 5.1 – Platform” white paper that introduces the new Auto Deploy Stateless Caching and Stateful Install modes. You can download the white paper from here.
vSphere 5.0 introduced VMware vSphere Auto Deploy, a new way to rapidly deploy new vSphere hosts. With Auto Deploy, the vSphere host PXE boots over the network and is connected to an Auto Deploy server, where the vSphere host software is provisioned directly into the host’s memory. After the software has been installed on the host, it is connected to the VMware® vCenter™ Server (vCenter) and configured using a host profile.
Auto Deploy significantly reduces the amount of time required to deploy new vSphere hosts. And because an Auto Deploy host runs directly from memory, there is no requirement for a dedicated boot disk. This not only provides cost savings, because there is no need to allocate boot storage for each host, but it also can simplify the SAN configuration, because there is no need to provision and zone LUNs each time a new host is deployed. In addition, because the host configuration comes from a host profile there is no need to create and maintain custom pre- and postinstall scripts.
Along with the rapid deployment, cost savings and simplified configuration, Auto Deploy provides the following benefits:
• Each host reboot is comparable to a fresh install. This eliminates configuration drift.
• With no configuration drift between vSphere hosts, less time will be spent troubleshooting and diagnosing configuration issues.
• Simplified patching and upgrading. Applying updates is as easy as creating a new image profile, updating the corresponding rule on the Auto Deploy server and rebooting the hosts. In the unlikely event you must remove an update, reverting back to the previous image profile is also easy: 1) Reupdate the rule to assign the original image profile and 2) do another reboot.
NOTE: Because an Auto Deploy host runs directly from memory, it often is referred to as being “stateless.” This is because the host state (i.e., configuration) that is normally stored on a boot disk comes from the vCenter Host Profile.
In vSphere 5.0 Auto Deploy supported only one operational mode, which was referred to as “stateless" (also known as “diskless”). vSphere 5.1 extends Auto Deploy with the addition of two new operational modes: "Stateless Caching" and "Stateful Installs".