I had only one SCSI controller, an mpt(4), so scsibus0 at mpt0 and sd0/1 at scsibus0.
Now, I have an additional mpii(4), and mpii0 attaches before mpt0 (despite the order in config being the other way round) and I get scsibus0 at mpii0 and scsibus1 at mpt0, thus my former sd0/1 become sdn/n+1, with n being the number of drives attached to mpii0/scsibus0. Is there a way to steer the order of attachments?