Every time they get into one of these 12 hour plus upgrades I find myself wondering what exactly they are doing. I have about 30 years IT experience and 15 years in large distributed systems using Oracle.

Patching / imaging the actual realm server CANNOT take 12 hours. If it does they are doing something very wrong.

So it comes down the the database server(s). It has been documented that WoW is running on Oracle databases.

I have also seen that there is one big ass database server per data center, not a database per realm, and common databases where you need cross realm support like BG and instance finders.

Since Oracle is a shared storage architecture, meaning that it does not matter how many CPUs you add, they are all looking at the same hard drives...storage IO bandwidth always ends up being the bottleneck. That's the communication medium between the database servers and the database hard drives.

If Blizzard had more database IO parallelism, which can probably only be achieved by building out databases systems that are as heavy duty as the existing ones on a realm by realm basis, we would be playing right now.