Toshio, your comment below is [dead] so I can't reply, but the databases vary from 10's of GB to multi-TB depending on their use.
The DBs are often very write intensive on the master, with as much reading as possible done on slave databases, with tables heavily normalised to try and reduce the disk performance hit.
Most of the extremes of the setup are there for legacy performance reasons - The newer systems using SQL Server 2008 or 2012 and SSD drives generally don't need it, and we're moving towards a less normalised setup.
Also, since the entire discussion started by me questioning the reliability of sql server, can you say how many days your database server stays up between reboots?
The DBs are often very write intensive on the master, with as much reading as possible done on slave databases, with tables heavily normalised to try and reduce the disk performance hit.
Most of the extremes of the setup are there for legacy performance reasons - The newer systems using SQL Server 2008 or 2012 and SSD drives generally don't need it, and we're moving towards a less normalised setup.