Network Sherpa has been blogging up a total storm lately. Take this article on which is front or back when working out airflow and comparing three vendors approaches to how you choose the product:
What does front-to-back mean?
Using terminology like ‘front-to-back’ assumes a common understanding on where the front of the device is. I always thought the ‘front’ of a networking device was the bit with all the ports and blinkly-lights and stuff. Emm.. bad assumption.
Yep. Standards – you might think we have them. Cisco, of course, has the most people interfering with a simple design process. Combined with their habit of producing fifty SKUs for a product when five would be enough.
For the Cisco Nexus 3064 the ‘front’ of the device is the side with the fans, power supplies and management interfaces. The ‘back’ of the device as the side with the ports. Arrrggghh!! However, it does allow you to order the ‘default part code’ which has front to back airflow’ designed to be deployed in a TOR environment with it’s ports nearest the servers’ NICs.
Juniper, smaller team and more focussed but still ……
To tackle the front/rear ambiguity, Juniper uses the terms ‘port’ or ‘FRU’ side in the datasheet for the QFX 3500. For example a TOR would use ‘port-side exhaust’. Kudos to Juniper for ensuring there is no ‘default’ airflow assumed. It would be sweet if they would provide a master-SKU for each airflow option, rather than choosing it for every FRU type though.
Unsurprisingly, Arista shows that they can channel “common sense” instead of corporate marketing diffusion:
What about Arista?
I have to give credit where it’s due. Arista tackled this issue elegantly for it’s 7050 switch by explaining the options clearly. Like Juniper, they don’t assume any default airflow.
You are forced to make a choice between two master-SKU’s; DCS-7050S-64-F (front-to-back) or DCS-7050S-64-R (rear-to-front).
Arista also preserves the definition of ‘Front’ being port-side and ‘Rear’ being PSU-side.
Lastly, Arista uses color coded PSUs and fans using classic design principles. Red for hot (exhaust), blue for cold (intake). Then they show you a picture on their datasheet. Thank you Arista.
With pictures. Add Network Sherpa to your RSS feed. He’s got some great stuff going on.