automatic sleep on external USB disks?

[David Wetzel <dave%turbocat.de@localhost>]

Hi,

how can I set this disk to sleep after some time of inactivity and wake it up 
automatically?
It is connected to a ALIX board...

umass0 at uhub1 port 1 configuration 1 interface 0
umass0: Prolific Technology Inc. Mass Storage Device, rev 2.00/1.00, addr 2
umass0: using SCSI over Bulk-Only
scsibus0 at umass0: 2 targets, 1 lun per target
sd0 at scsibus0 target 0 lun 0: <FUJITSU, MHS2030AT, 8405> disk fixed
sd0: fabricating a geometry
sd0: 28615 MB, 28615 cyl, 64 head, 32 sec, 512 bytes/sect x 58605120 sectors
sd0: fabricating a geometry


Cheers,

David