Recently at work, I had to implement some functionality that required the use of Guid identifiers that were stored in SQL Server. The Guids were generated in the application and used as an alternative key / external identifier for other systems. To avoid excessive index fragmentation, we opted to use the GuidComb variant using a generator from the NHibernate project.

The GuidCombGenerator generates Guid values that have a timestamp embedded into the last 6 bytes. For example: