Why does it take so long to create a service definition?

[JonathanBailey]

I've created a map document in ArcMap 10.1 SP1, and from that I'm sharing it as a service definition. The data in the map document is stored on a shared drive (which happens to be on the same machine that hosts my ArcGIS Server instance). The data folder is registered with ArcGIS Server (using its UNC path). I'm saving the .sd file in the shared folder on the server.

Creating the service definition is taking forever (over 1/5 hours). Granted, the data source is fairly large, but since  it's not being copied to the server, what's taking so long to create the service definition?

Thanks,

Jon.

[AshanLazarus]

I am also expereincing this exact issue and would like to understand what causes it or if there is a better way of uploading new layers instead overwriting/making a new web layer as both those options take over a hour.