Questions[cooling](server)

I have a server motherboard in a large tower case with several hard disks installed. It's basically a media server that serves over CIFS.

I'm using the 'sensors' command on Linux to monitor the system temperatures. It typically runs around 70c, but if it gets a tough load (downloading several things, hashing the downloaded content) it can cause the fans to spin up to max. An first this would happen briefly, then the fans would spin down after the system cooled. Now, however, the fans never spin down and just howl at full speed forever until the system is shut down for a moment then booted again. Rebooting vs hard cycling the system, curiously, often results in the fans never leaving the "bad state" and they stay on full power.

Troubleshooting steps I've tried:

• Alter BIOS temp control settings
• clean and reapply thermal paste
• double-check fan header connections
• clean dust off internal components

I'm using:

• CentOs 6.8
• Tyan S8230 motherboard
• (2) 12-core Opteron CPUs
• (2) Small Noctua case fans
• (2) Generic, medium case fans that came with the case.
• (2) std CPU coolers that came with the CPUs

ipmiutil sel list output: http://sprunge.us/bJg0gM

I have been comparing our server room logs for power usage, compressor usage, and outside temperature and I'm not sure if something is wrong with my understanding how these systems work, or if something is wrong with our records.

• Hot day: +30C outside, ~50% compressor use, ~25 KW electricity use
• Cold day: -30C outside, ~50% compressor use, ~25 KW electricity use
• Inside it's constant 23C
• Equipment that this is cooling generates about 28 KW worth of heat as measured by UPS readout.
• This is an 20 year old Liebert 20T HVAC unit hooked up outside condenser.
• ~25 KW includes the condenser electricity use
• Compressor readings go in increments of 0,25,50,75 and 100%
• This Liebert has 2 compressors in it and from what I gather (maybe wrong?) each compressor has three speed modes. Off, Medium, High. So if two compressors are on medium that's 25+25=50% or if one is high and other medium that's 75%. If both are on high that's 100% readout.

I would think that on a cold day the compressor use should be way lower than on a hot day. I also assume that lower compressor utilization means large reduction in electricity use.

We have one reading per day (manually entered), and because the compressor use oscillates between 25 - 50 - 75 as it's internal thermostat tries to maintain 23C steady, it's possible that we were unlucky and we got reading during the very short time it was in the "up" part of the curve on the cold day. But I took averages of those numbers to eliminate that possibility. The 50% and 25 KW are averages over multiple days. I rounded them (+/-10%) for the purpose of of highlighting that they are essentially the same. The effect I'm looking for is 30% to 80% difference due to temperature. On the really cold day wouldn't the cooling be essentially free?

Are my readings wrong or am I completely wrong in my assumption that there should be massive power savings during cold weather with this kind of system?

To maximize convection cooling in a rack, does it make a difference whether the hottest items are at the top or bottom? If so, which produces the most cooling and why? Please limit answers to ones based on facts or industry-standard design principles rather than speculation, opinion, or personal choice.

Please note for this question I want to focus purely on the effect of the placement of the items on convection-only cooling. Please ignore other considerations, such as weight distribution or use of fans.

I am looking for a database that has high and critical temperatures listed for CPU's and GPU's, or a tool that will be able to extract this information.

Google is filled with 'my gpu runs at 63C, is it too hot?' and long pointless discussions that talk about their temperatures and setups.

What I am looking for is data that clearly shows at which temperatures various hardware attempts to down-clock itself to cool down and at which temperature it shuts off.

Looking for first hand experience with an AcoustiRack. Noise is fairly important. The main concern is heat. The unit will have a few Dell servers r510, r620, VRTX fully loaded, 2 APC UPS 2200va.

Any other suggestions for a rack that can house this configuration within an office would be great.