This is a quick consideration about using id of type GUID in nhibernate. If in SQL server the cluster index is on the id (default choiche), if you use a simple guid generator you will end in high index fragmentation. This happens because if you insert a lot of objects into the table, since the physical ordering of the records (the clustered index) is on the Id field, inserting a sequence of objects with random id will insert these object randomly into the physical space of the DB. Remember that the index is a Tree that was kept ordered by its clustered index.
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