The 7504E was introduced in 2013 and entered legacy status in 2016 with the introduction of the 7500R series.
Each line card has six packet processors. Each processor has 3 Gbytes. The same line cards are used in the 4- and 8-slot switches.
Wondering whether Arista queue sizes were defaults or are user-adjustable, I asked their TAC. TAC responded via email on 8/6/13:
You can indeed change the voq limit on 7508 with the following command: "platform petraA voq tail-drop (value between 1 & 50 megabytes)". The effective changes can be observed under "show platform petraA buffers" as (For example, when the value is kept at 5 megabytes):
VOQ Limits (bytes) Normal : 5242880Arista commissioned a microburst test for the 7508 as part of a review from NetworkWorld in 2012. The results are much less clear. Key points are:
Massive overload of all the paths through the switch will cause most of crossbar arbitration requests to fail. A scheduler that can handle a credible overload may crumple into a whimpering ball on the floor. Most of the time, most of the input queues are empty and the scheduler can bypass them to focus on queues that contain traffic. But NetworkWorld's steady-state test fills all the queues simultaneously. If failed attempts to thread a packet through the switch fabric have the same cost as a success and the failure rate is pushed to astronomical levels, the test has nothing to do with reality.
What this really demonstrates is the first bullet above. There are no standards for a microburst test. And when engineers try to make up a test designed to fit the test equipment on their bench, the results are not good.
Architecture talkHugh Holbrook gave a talk at Networking Field Day 10 in August 2015 with title 7500 architecture and Why Buffers Matter. It is about 30 minutes.
In the talk