Low temperatures cause slow sata write performance

hi, i am having a really odd issue regards LOW temperatures and need some advise. i have a Asus M5A78L-M LX v2 motherboard and am using this as a server in my garage running unRAID. i am seeing slow write speeds to ALL sata drives when the machine is located in the garage, if i being the unit into the house then im seeing normal write speeds. at first i thought this might be to do with networking, so tried changing the cable, changing the switch, and changing the nic with no result.

i then found out the issue is related to temperature, the ambient temp in the garage is around 10C at the moment, whereas my house is around 20C, i stumbled across this my noticing the write speeds were actually good whilst in the garage after being in the house, but only for a short period, so it looks like as soon as the unit cools down enough performance takes a nose dive again.

so the million dollar question(s), firstly is this a mobo issue or is this a psu issue? (psu is corsair CX430), second question, if this is a mobo issue how do i stop the mobo changing the sata speed, ive tried switching off cool and quiet and ive tried disabling Q fan with no result. ive been googling this for days but cannot find anthing regards cool temp, only issues with too higher temp!.

any help VERY much appreciated.
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More about temperatures slow sata write performance
  1. Well the way high speed interconnects like SATA work is they depend on good, consistent connections between the cable and the connector on the motherboard/HDD. So when the temperatures reach high or low extremes the connectors can swell/shrink respectively in size and go "out of spec" in the quality of the contact causing transmission line characteristics to deviate and errors in the communication.

    I'm not familiar with the SATA protocol but if its like other protocols then when errors happen, it simply tries over and over until the data reaches the destination and is verified correct. This COULD account for the slowdown in the communication (constantly stopping to resend data). However, I am inclined to think that a temperature of 10C (50F) is well within spec of such a cable unless it has been damaged or the build quality was very poor. You could try another cable to be sure, grab the nicest SATA cable you have and try it. If its a fanout cable from a raid card purchase from the raid card vendor only or approved vendors and try to avoid ebay knockoffs (they can be out of spec straight from the factory). The places most likely to introduce a problem are at the connectors. It is very unlikely that the defect, if there is one, is present along the length of the cable unless it has been visibly damaged.

    So in conclusion, while it is possible that the temperature is causing this grief i'd be a little surprised (not very, mind you) if it was found to be the culprit. Try more cables and see how it behaves. Perhaps there is a way to see what drive is causing the errors? I know of no such way but its worth a google.

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