Specs like "6A MOSFET" don't exist in isolation. The current rating of that MOSFET is due to the on resistance(Ron), the resistance between source and drain. As current flows through the FET this resistance causes power to be dissipated as heat. The 6A number comes from how much heat the junction can handle without frying and is measured under a set of assumptions.<p>Usually testing is done at room temperature (25C often used) with the best possible heat-sinking and ideal Vgs. Most MOSFETs of this type actually tie the internal thermal components to the drain pins. Its intended that the PCB designer use a large copper pour for the drain pads, this copper area acts as the heatsink for the chip, transferring heat away from the junction.<p>In other words, the MOSFET can only handle 6A if ambient temperatures are kept at room temp (usually means fans on it or its wide open to a room), there is adequate heat-sinking provided by the PCB design, and Vgs is high (higher Vgs reduces Ron). Further its important to remember that FETs have a "run away" characteristic in that as junction temperature rises so does Ron, which creates more heat.<p>So, there is a lot more to the functional rating of a MOSFET than the 6A on the datasheet. In reality you would never want to nor expect that FET to hold 6A. With just a cursory look at the PCB layout and previous experience with what the ambient temperatures tend to be on back-planes of server chassis loaded with many drives, 1A would be pushing it, so I'm not at all surprised that these things blew.<p>Perhaps the most WTFery aspect of that PCB is the lack of any suitable capacitance near the SATA connectors. If you aren't using staggered spin up and many drives were spinning up at the same time the rail voltages can dip which in this setup causes Vgs to drop, increasing Ron at the worst possible time as mechanical drives draw a lot more current at spin up. This could trigger thermal run away.
I'd honestly never heard of Norco, but that's because Supermicro tends to be awesome.<p>They're essentially the OEM for a lot of Intel developer stuff now, too. Over the past 10 years, they went from "yet another commodity motherboard manufacturer" up to being the big white box option. They have basically replaced Dell and HP as the go to vendor for a lot of big deployments, although Dell and HP do better financing, Dell and HP have a few higher end products, and Dell/HP have better desktop/workstation/laptop products if you want a full suite from one vendor.
This may be a newbie question.<p>Article states: "... it should work fine in any metal box, right?"<p>But then says the <i>case</i> had some electronics which failed. Which means it wasn't just a metal case. Anyway TIL that server cases aren't just metal boxes.<p>And in case somebody wants to respond, how important is vibration dampening to ensure hard disk reliability? What's the best way to damp vibrations in a consumer tower desktop case?
I think it's more 5-platter 7200rpm drives vs. 3T drives, inherently (I think there may be a 4-platter 3T now). An old 5-platter 75GXP might kill it, too.
The enclosure isn't usually something you think about that much as long as it has the requisite number of bays. The prospect of hooking everything up only to see the magic smoke get released is terrifying.
Everyone learns the cheap hardware lesson at least once.<p>"1% less downtime means 87 hours per year. Do you think Lenovo is 1% better than Acer?" <- what I say when I encounter a client that hasn't learned this lesson, and insists on low end gear.
We have a Norco 24-E which is not a system case, but an external drive enclosure with a SAS expander. I don't know if its the same backplane but I don't know why it wouldn't be. This article scared me because we have 24 SAS 15k rpm drives on it.<p>Then I checked the drive spec and saw that we are pulling 0.8A on the +5V rail and 1.2A on the +12V rail which is even more than these 3TB SATA drives without backplane issues for months.<p>We did have to upsize the case's PSU from the shipped 500W though as beyond 15 drives we got voltage warnings from the expander.<p>So I think YMMV.
I set up a Norco 4224 for backup purposes and plugged in a couple of 3TB WD green drives, and have not had any issues at all. Maybe the WD green drives don't require as much current as these ones?