Advantages and Disadvantages of a Two-Data-Center Architecture

The advantages of a two-data-center architecture are:

Lower cost.
Only two data centers are needed, meaning less space and less coordination between operations staff.
No arbitrator nodes are needed.
All systems are connected to both copies of data, so that if a primary disk fails, but the primary system stays up, there is no package failover.

The disadvantages of a two-data-center architecture are:

There is a slight chance of split brain syndrome. Because there are two cluster lock disks, you would get split brain syndrome if the following occurred simultaneously:
- All heartbeat networks fail.
- All disk links fail. The disk link from data center A to cluster lock disk B fails (see Figure 2-1 “Two Data Centers with FibreChannel Hubs”.) And the disk link from data center B to cluster lock disk A fails.
The chances are slight, however these events happening at the same time would result in split brain syndrome and probable data inconsistency. Planning different physical routes for both network and data connections or adequately protecting the physical routes greatly reduces the possibility of split brain syndrome.
Currently there is a maximum distance of 10 kilometers between data centers.
Mirroring increases CPU overhead.
Although it is a low cost solution, it does require some additional cost:
- FibreChannel links are required for both local and remote connectivity.
- All systems must be connected to both copies of the data.

Technical documentation