Optimal Setup für GMS 2014 R2 > 1000 Users

Hey guys,

in our current setup we have 2 GMS R2 Servers and 2 PO´s (1 GMS for one PO). But now we would like to add a 3rd PO with the benefits of the GMS.

1st GMS: 20 User (live)
2nd GMS: 150 User (live)
3rd GMS: 1500 User (future).

I checked the recommended Setup for the GMS. But there are only 750 Users. Is it possible to increase the RAM / CPU / HDD for the Setup with 1500 User?

Does anyone have experience with a higher load?