DSM-G600, DNS-3xx and NSA-220 Hack Forum

Hi all

I've just bought and set up a DNS 313 with Debian lenny as explained in this tutorial.
http://dns323.kood.org/forum/viewtopic.php?id=3007

It works great, except that hard drive never spins down.

Looking at /etc/rc.local, I noticed that the hdparm command included in the lenny package referenced in the tutorial is :
  hdparm -s 60 /dev/sda

but -s parameter is about "power on in stand-by" (PUIS), which doesn't concern spinning down in case of inactivity. So I replaced by :
  hdparm -S 10 /dev/sda

with a value of 10 or less because i want to be able to test quickly if drive correctly spins down. In this mode, hard drive is always on, even if i put a value of 1.

I tried to manually spin down the drive with
DNS-313:~# hdparm -y /dev/sda

Then, i can hear that the drive stops, and if i type
DNS-313:~# hdparm -C /dev/sda

/dev/sda:
drive state is:  standby

but a few seconds later (variable, between 10 an 70) , drive comes up again, and the same command gives me :
DNS-313:~# hdparm -C /dev/sda

/dev/sda:
drive state is:  active/idle

I supposed that it could be a consequence of some daemons, or swap activity, writing or reading periodically, so I killed some processes and ran "swapoff /dev/sda1" to try these tests this with a minimal set of processes,  but the hard drive still had the same behaviour. These are the processes running on DNS313 while i run these tests :
DNS-313:~# ps fax
  PID TTY      STAT   TIME COMMAND
    1 ?        S      0:04 init [2] 
    2 ?        SN     0:00 [ksoftirqd/0]
    3 ?        S      0:00 [watchdog/0]
    4 ?        S<     0:00 [events/0]
    5 ?        S<     0:00 [khelper]
    6 ?        S<     0:00 [kthread]
   12 ?        S<     0:00  \_ [kblockd/0]
   15 ?        S<     0:00  \_ [khubd]
   40 ?        S      0:00  \_ [pdflush]
   41 ?        S      0:00  \_ [pdflush]
   43 ?        S<     0:00  \_ [aio/0]
  657 ?        S<     0:00  \_ [ata/0]
  659 ?        S<     0:00  \_ [scsi_eh_0]
  662 ?        S<     0:00  \_ [scsi_eh_1]
   42 ?        S      0:00 [kswapd0]
  672 ?        S      0:00 [mtdblockd]
  901 ?        S      0:00 [kjournald]
  963 ?        S      0:00 [egiga0]
1082 ?        Ss     0:00 /usr/sbin/inetd
1138 ?        Ss     0:00  \_ in.telnetd: olivier-eeepc.lan
1139 pts/0    Ss     0:00      \_ login -h olivier-eeepc.lan -p
1140 pts/0    S      0:00          \_ -bash
1198 pts/0    R+     0:00              \_ ps fax
1126 ?        S      0:00 /usr/sbin/pbutton -s /bin/sh -e /usr/sbin/halt.sh
1127 ?        S      0:00 /usr/sbin/fancontrol -l 42 -h 48 -t 120
1137 ttySL0   Ss+    0:00 /sbin/getty 19200 ttySL0


I don't have any more idea at the moment to make the drive spin down.

My hard drive is a WD Caviar Green 500 GB WD5000AACS.
Do you have any suggestions ?

Thanks for your help.