The generic SCSI code (which is now used by the SPARC port, in addition
to the i386, Amiga, etc.) issues a SCSI `start' command, which should
cause the drive to spin up.  Unfortunately, it doesn't wait and will
probably time out too quickly on the next command.  There needs to be a
loop that polls and waits several times for a total span of, say, 15
seconds.