Hello Jeroen_D,   I'm sorry to see you had the breaking mirror issue with the IDSDM firmware 1.15.  You have done the recommendation to rollback the IDSDM firmware to version 1.13  and then re-establish the mirror.     I thought there was thread discussing this issue but I was not able to locate it.  The issue does not happen to all systems or operating systems, but if it does happen to you then the rollback is the recommended action until next update is available.
Hello, Last week we did a upgrade, bios and firmware, on R640's servers with SD card mirrors. Upgraded versions bios 2.12.2 and ISDM1.15   Everything went well during the upgrade. But after +24h  later some hosts lost their SD card storage. After a reboot sd2 card was offline and the mirror was disabled by the bios. We could rebuild the SD mirror and sd2 was back online. But after a while the sd2, mirror failed again. We had to downgrade  all the hosts to previous versions get a stable SD mirror. Is this a know problem with ISDM1.15 or bios version?   BR        
R640 ISDM mirror breaks after upgrade ISDM firmware