Ok, re-biult the sd card... now, omv is booting without problems...
2 more questions, please:
1) I modified /etc/fstab as described for flash drives-plugin. But, do I need to activate the plugin itself afterwards ?
2) HDD /dev/sdc is pre-failing smart-test (raw_read_error)... don´t really know how to test the file system. And, if I want to replace the hdd: currently the raid 5 consists of 4 x 2GB WD red. Replacing the third 2GB-WD-hdd (sdc) with a Seagate Iron Wolf 4GB, for example, does not lead to a problem ? Just shutting down the ProLiant, replacing the hdd, booting it into OMV 3 and the RAID 5 will rebuild all automatically ?
Thanks in advance.