Edit / Conclusion:
These errors were intermittently being logged against drives in a SAS expander JBOD for writes only due to a mostly good, but partly bad port on an LSI SAS9206-16e card running IT mode P20.00.07 firmware:
mpt2sas_cm1: log_info(0x31120303): originator(PL), code(0x12)...
I'm migrating my NAS from a Rosewill RSV-L4500 to a Supermicro 847BE1C chassis. This is the one I will use:
I will reuse the the cpu, memory, SAS HBA, and disks from the current system.
Motherboard: Supermicro X10SLH-F
HBA: IBM M1015