Greetings.

Recently I purchased a My Book Studio 500 GB external HDD. It came pre-formatted with some Mac file system that I replaced with XFS. I wanted to use this HDD as a networked storage drive and I decided to have it plugged onto my 24/7 server. The HDD comes with 3 different ports to connect it to a PC - Firewire, USB and e-SATA. So I thought I'd buy a new fancy Firewire PCI card and plug it into an empty PCI slot. The PC I use for my server is an old Pentium 300MHz running Ubuntu Server 7.04. Everything fine and well. I power-on the PC, wait until it boots and connect the HDD via Firewire. The HDD powers on by itself.

Now at this point there is some shell output that gets printed twice:
[4406.125386] sda: assuming drive cache: write through

Anyway, by doing mount -t xfs /dev/sda1 /mnt/disk I can successfully mount and access the hard drive. Now here's the thing. After unmounting the drive I thought I'd give it a try to stop it with "sdparm". So I issue a command under root like "sdparm --command=stop /dev/sda" which, for some reason, fails. Using the command "sdparm -v /dev/sda" outputs the following lines:

/dev/sda: WD --- My Book --- 1018
Request sense cmd: 03 00 00 00 40 00
Request sense: Fixed format, current: Sense key: Illegal request
Additional sense: Invalid command operation code
REQUEST SENSE failed

The same gets printed when I add commands like --command=start, --command=stop, --command=sync. I haven't tried other commands. So I'd like to know how to fix this. What could be wrong? I can confirm that there is nothing wrong with the HDD as issuing the same shell commands from another PC with Slackware on it works without any complications. The disk spins down nicely.

Any ideas?