The approach to making service applications and services highly available in a SharePoint farm is typically simpler than ensuring the Web Front End or database tiers are highly available. In most cases, for a service application or service to be highly available, you must start the service instance on more than one server. SharePoint will then utilize multiple servers running the service automatically. You can start service instances by using the Service on Server page in Central Administration or by using the Start- SPServiceInstance PowerShell cmdlet.
There are some service applications or services that cannot run multiple instances or require more advanced configuration to achieve high availability. These service include:
- Search service. In order to make the search service application highly available, you must configure the service application topology using PowerShell. Search is comprised of crawl and query functions and you must determine whether you require high availability for both functions.
- User Profile Synchronization service. You cannot run multiple instances of the User Profile Synchronization service in one farm concurrently. If you require the User Profile Synchronization service in your farm, you should consider a warm standby approach as best availability for this service