ReadyNAS appears to boot by itself

That is definitely the right supply. The switch and power socket you can see on the outside of your NAS are not the ones on the supply itself. You will also need a 6" extender for the ATA power connection (unless you want to cut off and splice in the original cable). I also cut short the other cables and installed the 90° connectors from my original supply (since it was totally gone). If you want to keep the old supply intact as an emergency spare, you can find the 90° Molex connectors on eBay. You could just use the ones pre-installed on the replacement, but that will leave you with a lot of extra wiring in the chassis.

Thanks for the support. I did reach the people at Netgear and they wanted nothing to do with me and anything that is out of the warranty period. I'm not sure how to go about replacing the power unit. It does seem like there are a lot of wires in the harness going into the power supply. I told the customer service rep that I'd be more than willing to pay for them to replace the power supply and they told me no.

So, I've had no auto reboot since my last post and the unit seems fine. But it continues to spin the fan fast (>2000 RPM) and loudly every 10 or 15 minutes for several minutes and then drops back to <1000 RPM.

I don't think I'm up to the replacement project myself. I guess I don't understand how this can be the correct power supply when the on-off switch is not located on the correct side of the unit.

My Pro6 was doing the same when using old seagate drives. Those drives tend to get hot, the fan does not spin up till a certain temperature is reached. At that point the fan spins up and it manages to reach full speed since it takes a few minutes for the drives to drop their temperature. I feel the algorithm behind this behavior is wrong: you don't spin up to full power just because one drive is 1°C beyond the threshold temperature.

Can you monitor the temperatures and see which one is going beyond the threshold level (drives, CPU, chassis)? Is there anything you may have missed when cleaning the unit? Are all fans spinning ok? I think I recall that the threshold for a drive is 38°C - may be wrong. But if you observe the temps, you'll find the pattern quite quickly.

Since I moved to WDC drives, they never goes beyond the threshold temperature and I've never heard the fan speeding up.

I had never thought about the drive types and temps. They are all 3TB drives.

I have four Seagate 3TB drives (ST33000650NS) and one WD (WD30EFRX, I think that's a "red.") The Seagates have between 15,000 and 18,000 hours on them and the Seagate has about 6,000 hours.

Generally the Seagates are between 38C and 42C. The WD barely gets to 32C.

Do you think that the more frequent higher fan speeds are the result of the drive manufacturer's higher temperatures? I'd hate to spend the money on replacement drives just to experiment.

Thanks for your input. It's something to think about.

I had Seagates on my NAS. They were going over (I think) 38°C every now and then and the fan would spin up. After a while the temp would drop below 38°C and the fan would slow down.

WDC are cooler - that's why I got them - and the fan never spins up. Keep an eye on the HDD's temps, you should be able to see the fan spinning up at a specific temperature.

The question is: you said it was not doing that before, did you replace the drives recently? Or did you upgrade the software? I feel the fan management is poorly implemented. If the temperature rise over the threshold, you would expect the fan to speed up a little to catch up, not to reach full speed till the temperature has dropped again - or at least to further speed up after several minutes, to allow the drive to cool down.

Let us know.

Some drives operate normally at a higher temperature range than what is safe for some very old drives which does complicate things somewhat.

if the 38 degrees figure I have on my mind is correct, that is not "high temperature". I kind of agree with try and keep the drives cool - even though Google demonstrated that the contrary will in fact extend the drives' life. What I don't agree with is the algorithm implemented.

Say the threshold is 38 degrees, the fan begins spinning up at 38.1 degrees, It then speeds up more and more till the temperature drops below 38.0 degrees again. That means that the fan will reach max speed after a few minutes if the drives are still at 38.1 degrees!

And BTW, this is only the chassis fan, the CPU fan reacts in a more logic way if memory serves.

EDIT: BTW, it must be more than 38°C, I've put a plastic bag in front of the NAS, took a long time to reach 38°C and the fan is not speeding up. Maybe it was 42°C? Sorry, it was some time ago.