Here is the summary information that I got from Huawei GTAC.
The switch has no any ingress buffers. The whole switch has 2.5 MB of interface buffer space for egress buffering. Each 10GE interface as well as 1GE has 8 egress queues. By default each queue has 6.25KB of buffer statically alocated to them, so summary we have 50KB per each interface.
If you install an extension card into S5300 then new interfaces will share the same common buffer pool and grab 50KB per each interface. Even when interface is shut down it still holds it’s 50 KB reserved.
Since the size of default interface buffer is quite small there can be buffering issues leading to packet drops when the buffer space is exhausted. You can release buffer space that is hold by unused interfaces:
interface GigabitEthernet0/0/5 shutdown qos queue 0 length 0 qos queue 1 length 0 qos queue 2 length 0 qos queue 3 length 0 qos queue 4 length 0 qos queue 5 length 0 qos queue 6 length 0 qos queue 7 length 0
This configuration returns 50KB of buffer space into common pool. Then you can increase queue length on a highly congested or bursty interface:
interface GigabitEthernet0/0/2 qos queue 0 length 500000
It is possible to know the size of buffer space available in common pool:
sys Enter system view, return user view with Ctrl+Z. [hua-hua]int g0/0/10 [hua-hua-GigabitEthernet0/0/10]qos queue 0 length 1000000000 Error: This queue support the length range of (0~1134208) [hua-hua-GigabitEthernet0/0/10]
I intentionally try to configure huge buffer size and get CLI hint revealing real buffer space available: 1134208.