A customer using an IBM System Storage DS8700 is facing performance problems. After the analysis by the technical specialist， the diagnosis indicates that the cache hits may be improved by a cache upgrade.  How can the system be monitored in order to check the benefits of the cache upgrade（）

• A、using the "vmstat" command on the AIX servers connected via SAN to the DS8700 system
• B、look at the IOPS using the DS8700
• C、reading the performance reports via Tivoli Storage Productivity Center for Disk
• D、generating reports using theTotalStorage Expert