For a new system, your IBM® marketing representative can help you analyze your system storage requirements. For an existing system, the current amount of data in the disk pool that is being planned is a useful starting point. The Display Disk Configuration Capacity option of the dedicated service tools (DST) or system service tools (SST) shows the total size (in millions of bytes) and the percent of storage used for each disk pool on the system. Multiply the size of the disk pools by the percent that is used to calculate the number of megabytes of data currently in the disk pool. In planning future storage requirements for a disk pool, system growth and performance should also be considered.
The planned amount of data and the planned percent of storage used work together to determine the amount of actual auxiliary storage needed for a mirrored disk pool. For example, if a disk pool is to contain 1 GB (GB equals 1 073 741 824 bytes) of actual data, it requires 2 GB of storage for the mirrored copies of the data. If 50% of storage use is planned for that disk pool, the disk pool needs 4 GB of actual storage. If the planned percent of storage that is used is 66%, 3 GB of actual storage are required. One gigabyte of real data (2 GB of mirrored data) in a 5 GB disk pool results in a 40% auxiliary storage utilization.