windows services - "Automatic" vs "Automatic (Delayed start)"

Question

When installing Windows services there are two options for automatically starting a Windows service on Windows startup. One is Automatic, and the other is Automatic (Delayed start). What is the difference between these two in detail?

For example, if you're creating the installer with wixtoolset, the ServiceConfig element has the DelayedAutoStart attribute. How will that effect what happens when services are started at boot time?

WiX documentation: ServiceConfig Element

Answer 1

In short, services set to Automatic will start during the boot process, while services set to start as Delayed will start shortly after boot.

Starting your service Delayed improves the boot performance of your server and has security benefits which are outlined in the article Adriano linked to in the comments.

Update: "shortly after boot" is actually 2 minutes after the last "automatic" service has started, by default. This can be configured by a registry key, according to Windows Internals and other sources (3,4).

The registry keys of interest (At least in some versions of windows) are:

• HKLMSYSTEMCurrentControlSetservices<service name>DelayedAutostart will have the value 1 if delayed, 0 if not.
• HKLMSYSTEMCurrentControlSetservicesAutoStartDelay or HKLMSYSTEMCurrentControlSetControlAutoStartDelay (on Windows 10): (DWORD) decimal number of milliseconds to wait, may need to create this one. Applies globally to all Delayed services.