I beg to dif­fer. This post is high­ly rel­e­vant for peo­ple which work with FreeB­SD since a not so short while and know about the rec­om­men­da­tion to dis­able the write caches of disk dri­ves to have an accept­able behav­ior in case of a power-failure. There are many peo­ple out there which know about this and dis­able the disk-cache as one of the first things.

BTW: the han­dling of the disk-caches os not relat­ed to GEOM at all, this is some­thing the ATA/CAM sub­sys­tems are respon­si­ble for. There was even a short moment in time where sos@ switched the default in the ATA dri­ver to dis­able the caches by default (IIRC he had to revert it because too much peo­ple had the opin­ion that performance(-reviews) are more impor­tant than data-consistency). AFAIK CAM (the SCSI side of it) does not even touch this set­ting, as it is a prop­er­ty of a dri­ve (a set­ting in the dri­ve), so you get what­ev­er the dri­ve ven­dor has set as factory-defaults (most prob­a­bly the write cache is enabled).