Mirrored protection normally requires additional disk units and input/output processors. However, in some cases, you might need additional hardware to achieve the level of performance that you want.
Use the following information to decide how much extra hardware you might need:
Mirrored protection causes a minor increase in central processing unit usage (approximately 1% to 2%).
If you have mirrored protection, you need to increase the size of your machine pool. Mirrored protection requires storage in the machine pool for general purposes and for each mirrored pair. You should expect to increase your machine pool by approximately 12 KB for each 1 GB of mirrored disk storage (12 KB for 1 GB disk units, 24 KB for 2 GB disk units, and so forth).
During synchronization, mirrored protection uses an additional 512 KB of memory for each mirrored pair that is being synchronized. The system uses the pool with the most storage.
To maintain equivalent performance after starting mirrored protection, your system should have the same ratio of disk units to I/O processors as it did before. To add I/O processors, you might need to upgrade your system for additional buses.
Because of the limit on buses and I/O processors, you might not be able to maintain the same ratio of disk units to I/O processors. In this case, system performance might be less.