Sometimes disks have data or meta data on them that prevents them from being used. This command will wipe the disk completely.
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wipefs -fa /dev/sd?
Sometimes even this fails. Try this:
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sgdisk --zap-all /dev/sdx
readlink /sys/block/sdx
echo 1 > /sys/block/sdx/device/delete
echo "- - -" > /sys/class/scsi_host/host5/scan