I have a one-time process (hashing all our user passwords) written using datasets. The performance needs improvement so we've profiled the application and found that increasing the 'batch size' of the update will improve performance. I also know that if I load the entire data set into memory the application will start hitting swap and slow down.

The question is: how big is a System.Data.DataRow derived class? I'd like to calculate a batch size which I know won't force the application into swap.