To force a rescan on a scsi bus (and each sata port appears as a scsi bus) and find new drives:

echo "0 0 0" >/sys/class/scsi_host/host<n>/scan

where <n> is the bus number

To remove a device

echo x > /sys/bus/scsi/devices/<n>:0:0:0/delete

Issuing these commands should cause the appropriate entries in /dev to come and go.