Isn't IPv6 widely deployed in china? Most major bittorrent clients have partial or complete IPv6 support these days - although IPv6 DHT support is still lacking apart from Transmission and BiglyBT.
But I don't know about the state of things of the multi-network clients which are popular china.
I am curious, what kind of write characteristics can manage to saturate a 255s timeout on a storage device that does 10k+ iops and gigabytes per second throughput? Normally writes slowing down leads to backpressure because the syscalls issueing them take longer to return.
I can imagine some crazy random access, small-record, vectored IO from large thread pools. But that's not exactly common because most software that is IO-heavy tries really hard to avoid these things.