Hi Alex,
Here are some reasons why you might want to configure multiple instances of NAV on the same Server machine:
1. Resilience: i.e. if you spread users across multiple NAV Services (NSTs) and one NST crashes then only a subset of users are impacted.
2. If you want to support multiple authentication methods for Users, e.g. One NST for NAVUserPassword authenticted users and another one for Windows users.
3. You may want separate NSTs to have flexibility with how you configure the service for different requirements, e.g. One NST for batch jobs requiring a smaller data cache size and a separate NST for Users.
4. With very old versions of NAV the NST was written as a 32-bit application so you would need multiple NSTs to scale up the number of users due to the RAM constraints with 32-bit apps. Modern versions of NAV have a 64-bit NSTs so this reason is no longer a factor.
You may not get any performance benefit per se from configuring multiple NSTs.
See here for the NAV/BC Performance guide which may be of assistance more generally with performance issues: docs.microsoft.com/.../performance-overview
Also, there are Dynamics partners available who can provide specialist performance advice for Dynamics NAV deployments if required.
