Servers in short depth racks with no rear perforation?

Discussion in 'DIY Server and Workstation Builds' started by frogtech, Aug 3, 2018.

  1. frogtech

    frogtech Well-Known Member

    Jan 4, 2016
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    Looking for any experiences, I've planning out a VSAN cluster build and want to use either SuperMicro 514 or 515. They're short depth 1U chassis, the main difference is the placement of the IO.

    On the 515, the IO is at the front and the fans are at the rear. The airflow is front to back and not rear to front. (so think pulling air through the heatsink instead of traditionally pushing air to it)

    On the 514, the IO is at the rear and the fans are at the front. The airflow is front to back.

    I was planning on using a short depth rack, so probably a 20-incher or one of the network cabinets. However it looks like those all have solid rear panels.

    Anyone know if:

    • the servers would be starved for fresh air and if it would impact temps in any significant way going with the 515 since the fans are rear mounted and pulling air instead of pushing?
    • Would I be recirculating warm air if I went with the 514 for front mounted fans?
    • Would it be better to use the rear of the 515 as an intake, rotating the fans around so they're blowing air over the system instead of pulling it?

  2. dandanio

    dandanio Member

    Oct 10, 2017
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    Recirculating warm air is a big problem with small cases and tight spaces (Rhyming!). Anyway, since I do not know your reasons to go with solid back panels, I would stay clear of that idea. Heated air rises and creates a convection cycle. I would supplant that naturally occurring cycle with a FAN or TWO on top above the servers (to pull the air UP) and you should have a relatively cool systems. Let us know what your reasons are.
  3. frogtech

    frogtech Well-Known Member

    Jan 4, 2016
    Likes Received:
    Well, I am not particularly going out of my way to look for racks/cabinets that have solid back panels, it just so happens that most of the shorter depth racks are meant to be wall mounted, and even if they can accomodate shorter depth servers/switches, the rear panel is still solid without ventilation.

    If my servers have fans that are mounted in the rear of each chassis, but push air towards the front of it and subsequently out of the front ventilation, would that be okay as well?
  4. Netwerkz101

    Netwerkz101 Active Member

    Dec 27, 2015
    Likes Received:
    You kinda still have the same issue but in reverse.
    You need cooler air to come into the back of the chassis - so no obstruction and enough clearance at back of rack.
    You would need all servers to have same direction of air flow (back to front) or at least place the servers with back to front
    air flow at the bottom of the stack (servers with front to back airflow above or top).

    This would prevent expelled hot air from (front to back airflow) servers being sucked into
    the (back to front airflow) servers.

    I don't know how creative you want to be with this setup, but I can visualize:
    - Rack with no back panel - simply don't install it or cut it out.
    - Rack with perforated back panel - make your own vent holes.

    With either of the above: create a channel for air behind the rack using 2"x2" boards if needed.

    Don't forget that aside from the rack, you have to consider the components going inside the 1u chassis.
    You didn't mention if you were using Atom (low watt/TDP) based equipment or Xeon (higher watt/TDP).
    I guess those high RPM/CFM fans should take care of a wide range of CPUs.
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