SATA Anatomy, Failure Anatomy

It’s best to start first with a quick history lesson on the SATA design, as it hasn’t been static through the years. It has gone through some important revisions - some visible and some not – that have shaped the SATA connector in to what we see today. We’d also like to thank Knut Grimsrud, chairman of the SATA International Organization and Intel Fellow in their Technology & Manufacturing group for helping us out with this article and answering some of our questions.

First and foremost, the SATA-IO identified issues early on with the design of the SATA connector, and has revised it several times. This is most obvious in the move from the SATA 1 motherboard connector to the SATA 2 motherboard connector, where the SATA 1 motherboard connector was far more exposed than the SATA 2 connector. This switchover was particularly evident on boards using both native and external SATA controllers, where one would be SATA 2 compliant and the other SATA 1, requiring the different connectors.

The SATA 2 motherboard connector added shrouding around the connector, which significantly improved the durability of the connector as the shrouding prevented cables from easily bending the wafer part of the connector. Unfortunately this kind of shrouding couldn’t be added to SATA devices, because the standard was designed for use in small devices that don’t have clearance to fit a full shroud. This results in the modern half-shroud design for devices, where the top-half of the connector is shrouded by the device but not the bottom half.

The other significant changes in the standard since its inception have been latching and chamfering. Most SATA devices now have recesses in their top side shroud that allow barbs on SATA cables to latch in to in order to provide downward stability since the underside is the unshrouded side. Chamfering has been added to the square edges of the tongue, and while not a visibly dramatic change, we’ve been told this is one of the primary improvements in strengthening the SATA connector.

Yet in spite of these changes we’ve still managed to do something wrong and break the connector on our hard drive. For the reason why, we’ll start with case designs and cable designs.

Part of our problem can be attributed to the amount of space we have to work in with the case involved in this investigation, the Antec P182. The P182, like many other cases, doesn’t leave a lot of space behind the primary hard drive bay. For most cases this is because there are motherboard components and cards in the way, while with the P182 it’s a matter of a 120mm fan being located behind the hard drive bay, which helps pull air through the lower chamber. Either way, with this specific case, we measure that we have about 2” between the rear end of a hard drive and the fan, which is very little space to work in.

We then come to the cable, in this case it was a bog-standard cable that came with one of the products we’ve used over the years. As we mentioned earlier, SATA cables aren’t quite as flexible as PATA cables when it comes to longitudinal bending, and while we can technically bend a cable completely over at any location, this isn’t great because it causes the cable to pull back in to a more relaxed position. From the tip of the connector, the cable we measured needs about 2.5” of space to bend comfortably.

With the amount of clearance we have being less than the amount of space to need to ideally bend the cable, it becomes obvious that this will quickly become tricky. We need to bend the cable at a sharper angle so that it stays well clear of the fan, which means it’s going to be exerting some force on our hard drive, a generally acceptable but not ideal situation.

And then finally there is the layout of the P182’s hard drive bay. The P182 requires the hard drives to be installed in to the cage at an angle, such that they are on their sides with the bottom pointing towards the bottom of the case, which you can see here. Keep in mind the fact that the top hard drive is on the opposite side of the case from where the motherboard is.

In this combination, we have the anatomy of our failure. Our cable is putting force on the SATA data connector towards the bottom side, which as we covered earlier is the weaker direction to go because it’s not shrouded like the top side is. Furthermore we’re using a SATA-1 style cable without a latch, which means we don’t have said latch to reinforce the connection. It turns out that this is enough force to break the SATA data connector on our hard drive, and when the drive cage was being secured one day the connector broke.

Index Resolution, Prevention, and Closing Thoughts
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  • FUXX - Friday, January 18, 2008 - link

    You could try swapping out the controller card on the hard drive. I've had pretty good luck doing this on a Seagate 80GB drive and a Maxtor 200GB. After an electrical storm I thought the drives were toast but after a controller card swap I was able to recover the data. Make sure to get the exact same controller though, it took me a while to find the proper one on ebay. Sometimes the same model hard drive would have different controllers depending on when it was manufactured. If you end up with the wrong one you might be hearing the click of death!

    Also, swapping hard drive platters is highly NOT recommended. :)

    Reply
  • yyrkoon - Sunday, January 20, 2008 - link

    I do not think they're worried too much about data recovery, and they probably know about swapping out the drive controller PCB already ; ) Works pretty good does it not : )

    Now to the article writer. Maybe it is because I tend to speed read articles as such most of the time(but I did read the article twice) it was not made clear to me, but did the data connector part of the PCB break off while moving the drive in or out, or did this happen while the drive was in already operational ? I just ordered one of these cases for myself(gun metal gray) and it would explain why I got a good deal on it after rebate if this is the case (sorry no pun intended). $45 for this case is not a bad deal, even after buying 4x right angle SATA connectors, but I would really hate to loose 3TB of data because all my HDD data connectors snapped off : /

    Another question I had, was do you think this could be brand specific ? I have a pretty good idea I know which drive you guys were using, and I do not use that drive, or even the same brand, but if this IS brand specific, I think your readers should know. At the very least the OEM should know, so they could fix this issue on future models.
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