UPS is beast in SharePoint 2010 world ( I don’t have to tell everyone knew about it) but guys let me tell you something after FEB CU 2012 UPS/FIM performance tremendously increased its way far better !!!!hmm what is the reason ? from FEB CU 2012 on wards FIM will use multi-threaded not single thread( surprised!! yes FIM was using single thread, serial processing but now that’s not the case), I’ve imported 2500 Users in less than 20 min WOW right!!. OK sorry for the off track let’s focus on the issue
“Error creating User profile service application- Failure retrieving application ID”
(Synchronization Service struck on starting)
This error in ULS is confusing and I see everyone say just redo all the stuff following best practice from harber but guys let me tell you this, if you have FEB CU 2010 or later and see this don’t worry just reboot the server where UPS is provisioned or check if Manage Meta Data Service is properly configured and check if its up and running, it you see MMS is configured then reboot and open CA site and check the Service status and give it atleast 5 min and you should see its started and everything should work as expected. ( No need to IISRESET after you see the service started , remember you already rebooted!!).