Is 45 degrees Celsius too hot for my disks? When my case is closed, the disks are sitting at 45c.  If I open the case and put a floor fan on them, they drop to around 32c.

It's not immediately fatal, but it's probably a little uncomfortable long term. Are you sure your case fans are oriented correctly? Many cases are designed for only one drive, and the fans are set to circulate air across the motherboard and video card instead of forcing air across the drives. All case openings other than directly in front of a fan or the drives should be sealed shut, and all fans behind the drives should be pushing air out, so as to force all fresh incoming air to flow across the drives first. If you want help with your fan layout, post a picture of your case with the side off, showing a clear view of as many of the fans and drives as possible. Some cases need help with airflow, cardboard baffles to force the air where you need it may be helpful.

@jonathanm Thank you very much for the feedback.

 

Here's my case: https://www.newegg.com/Product/Product.aspx?Item=N82E16811235056

 

Attached are pics of my tower.

That case should have a couple of fans installed in the front to blow cool air onto those drives, plus you can probably install one on the inside of that side panel.

 

I'd recommend something like this, but choose the size right for your case.

 

 

https://www.amazon.com/Corsair-Air-AF140-Quiet-Single/dp/B007RESGGC/ref=pd_sim_147_1?_encoding=UTF8&pd_rd_i=B007RESGGC&pd_rd_r=T9J0P3VJPABPW5NW0E1A&pd_rd_w=X8zNi&pd_rd_wg=7I4Dx&psc=1&refRID=T9J0P3VJPABPW5NW0E1A

AND get a can of compressed air and blow the dust off your cpu cooler and psu.

Id take off the front face plate and install the 120's to really keep that beast cool

 

http://www.zalman.com/images/productinfo/case/z11neo/Z11NEO_kor_08.jpg

Are the fans in the top and back both blowing out and the two side door fans beside the drives blowing in?

 

I'd take some clear packing tape and seal all the punched holes in the slot covers and the area above it, and any other vacant fan openings to keep air from leaking back into the case. Air will follow the path of least resistance, you need to force all the incoming air to flow over the drives.

Thanks @jonathanm @kizer @1812 @ashman70

 

I've added new fans, cleaned out the dust, and i'm running at an average of 36C now with the sides on the case.

That is a comfortable temp, good job.

Nice Job 

We really don't know what "too hot" is. And given the very small sample size we each individually have, we will never know the impact of a few degrees C on longevity, except anecdotally.

 

Best information I have read is that it is more the variation and frequency of temperature changes, rather than the absolute temperature, that does the most harm. So a drive running continuously at, say, 50C, might last longer than a drive being frequently spun down and spun up and vary in temperature from 22C to 40C repeatedly.

 

So it is hard to know. But my anecdotal experience is that cooler is better than hotter. And I'd consider 42C to be a pretty good upper limit for my hottest drive during a warm day parity check. Additionally, i try to have lengthy spindown intervals (5 hours), with the goal of not spinning up the same disk multiple times during a day. If the interval were 1 hour, I think I'd be spinning up my disks 3-4x as many times, with corresponding heating and cooling, and hurt the longevity. And anecdotally I believe my drives have held up well.