DST identification of disk controller cache failures without IBM i present

IBM technical support unable to diagnose failed disk controller cache failure on a brand new machine. Advised that support unable to diagnose without IBM i loaded and operating, during a risc-rick migration at the same OS level (V7.3) from POWER 7 to POWER 9 system. Moving from a system using HDDs to system that also uses HDDs. Could not determine problem cause and get IBM C.E. dispatched until RESTORE menu option 21 completed; this took 5 calendar days running non-stop. Once IBM i loaded, immediately identified hardware problem and hardware case A1CTGPV opened; C.E. dispatched with replacement hardware that ultimately resolve problem. We never did find a error report in DST "service action log" for this. The only clue way IBM i reporting the RAID set was "degraded". We looked for problem indications in DST/SST "work with disk" menus, no indication of "degraded" performance is show on "display disk configuraion" or "display disk parity" menu sets.

After loading SLIC, and in the midst of a VERY slow loading process, support was unable to guide us through checking for disk cache failure. We did not find, nor could hardware or software support provide a path in DST menus to determine if disk controller cache failure caused our symptoms. We were advised to allow restore to complete. IBM technicians stated they have a known problem determining issues with disk Cache in this type of migration until IBM i options have been loaded and OS is has ability to run "must gather" tools, or even look at WRKDSKSTS.