This section focuses on the mechanics of performing a backup of the server, using Out of Box (OOB) server tools for backups.
The System State Data (SSD) is an operating system layer that backs up the SharePoint server, which is crucial. It is not enough to just backup your data; the SSD backups maintain a copy of configuration and identity of the server. This includes the following files:
The registry
COM+ registration
Boot and system files
IIS meta-directory
In short, this is the most important type of backup because the SharePoint environment works from the SSD configurations. This data also needs to be in sync across all the server environments.
Service packs and hotfixes overwrite the system files; so changes to web configuration may cause an update in the meta-directory.