SCSI disks spinning down

[FreeBSD Questions]

I have a server, running FBSD 5.4, that has six SCSI disks in it.
It's primarily a fileserver for IT, and it's not access frequently,
but it does get some use.  Most of the time--any time it's been
sitting for a while and not accessed recently--reading from the drive
takes a few seconds.  I presume this is because the drive has spun
down due to it's idleness and the delay is because the drive is
spinning up again when I access it.  Is there a way to disable this?
The drives are IBM Deskstar drives (DPSS-318350M), and I don't know if
this feature is a feature in the SCSI subsystem somewhere on FBSD or a
jumper setting on the drive or what.  I'm not even sure I can turn it
off so the drives don't spin down.

Any ideas, anyone?

Thanks!