CentOS - Jun 2014 - external esata RAID box, how to spin down drives when idle?

I've posted before about my Venus DS3R Pro2, specifically in relation to 
using USB3.

But this a different topic about the same device.

It doesn't seem to do any power-saving on its own, i.e, the drives stay
spinning continuosuly, 24X7. Setting the appropriate power-save options
in the screen saver or power manager screens doesn't seem to have any
effect on these drives.

Wondering if anyone can suggest other ways to approach this? 

Normally it is idle for about 23H, 57M per day, as it only runs a short
backup session at 00:30, using rsnapshot which doesn't take very long
at all.

cat /proc/scsi/scsi reports:
Host: scsi6 Channel: 00 Id: 00 Lun: 00
  Vendor: ATA      Model: JMicron H/W RAID Rev: 0958
  Type:   Direct-Access                    ANSI  SCSI revision: 05

dmesg reports:
sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support
DPO or FUA
 sda: sdc1
sd 6:0:0:0: [sdc] Attached SCSI disk
...
EXT4-fs (sdc1): mounted filesystem with ordered data mode. Opts: 
SELinux: initialized (dev sdc1, type ext4), uses xattr


-- 
---- Fred Smith -- fredex at fcshome.stoneham.ma.us
-----------------------------
                       I can do all things through Christ 
                              who strengthens me.
------------------------------ Philippians 4:13 -------------------------------