GoFlex Net: powering a 3.5" SATA drive

[baafie]

There is a previous topic on this subject which has been closed (in the absence of a good reason):

viewtopic.php?f=53&t=1672

At any rate, I just wanted to mention that I came across this hardware hack:

http://wiki.openwrt.org/toh/seagate/goflexnet#info (scroll down until you see the 3.5" hack images)

I thought that would be of interest to people here.

It appears that the manufacturer has left the 12V lines on the SATA sockets unconnected, even though the stock power brick is rated for 12V-2A output. My GoFlex Net uses about 5W at the wall with a USB stick plugged in, which would leave about 19W for powering SATA drives. One could power two efficient SATA drives, and remain within the brick's power rating provided their spinup power requirements don't exceed 9.5W, which should be possible: https://www.cl.cam.ac.uk/~acr31/pubs/hy ... drive2.pdf ; or perhaps one 2.5" drive and one WD10EFRX, which requires 1.2A during spin-up. http://www.wdc.com/wdproducts/library/S ... 771442.pdf

I'd be glad to hear other people's views on the above.

[baafie]

I tried hooking up the +12V line as shown in the pictures linked from my previous post, and it worked like a charm. While I was there I disconnected the two LED capacity indicators that I wasn't using anyway, and that reduced the power consumption of the base unit from 5W to 4W.

For now I have a single WD10EADS drive hooked up. The power consumption of the GoFlex with this drive and a USB stick together registers as 7W idle, and 9W with read-write activity on the 3.5" drive.

[baafie]

One issue that I've noticed is SATA error messages popping up occasionally, such as:
$this->bbcode_second_pass_code('', 'ata2: SError: { Dispar }')
According to the libata docs these are indications of a 'bad or inadequate' power supply.

Given that the drive spins up without issue (when the power draw is highest) my guess is that the stock power supply is adequate, but perhaps the 12V line isn't stable enough.

Still, when such an error occurs the kernel resets the SATA port and the drive continues to operate without issue, so I'm not too worried about it. All the same, I'm not sure if this setup can be generally recommended.

Update: I resolved this issue. See below.

[baafie]

It was also suggested elsewhere that the SATA errors could be caused by a faulty cable, so I tried replacing it, and lo and behold, the errors have since disappeared.

So I have to alter my main conclusion: the power supply seems to be adequate and I can generally recommend the mentioned hardware hack.