I want to consolidate storage for the mainframe and open systems on the same box. But I'm not sure how the performance and overall operation of storage will be affected when I mix the two disk formats in the same box. What should I do: consolidate or separate the disks?
First, I would highly recommend that you read the excellent article "Modernize mainframe storage" by David Braue in the February 2003 issue of Storage magazine.
There are advocates of keeping mainframe storage separate from open systems storage, primarily due to management features for the mainframe side, and performance/caching advantages to leaving the mainframe storage separate.
However, with FICON connectivity to tie the mainframe into the SAN infrastructure, mainframe storage can be effectively consolidated with the open systems storage infrastructure, with the primary advantage of being able to get rid of aging, out-dated storage equipment and take advantage of the cost savings of consolidation and unified storage management. There are a number of excellent technologies out there. The successful implementation of such depends upon configuration variables and your company's application, backup, and performance requirements. In general, you'll find that this approach gives you a performance advantage. The use of FICON can reduce the cabling requirements significantly and provide a common connectivity platform for both mainframe and open systems storage. (This allows both types of servers to share tape libraries, mirror data locally and over distance via fibre).
Another point to consider -- if you are looking at Linux on the mainframe, you have the additional advantages of further connectivity options, greater performance (by eliminating signaling overheads) and being able to take advantage of upcoming technologies such as clustered file systems, which allow for a more efficient utilization of storage by eliminating the need to replicate data between z/VM nodes and non-mainframe cluster nodes.