Fetcher2 fetches far more slowly than Fetcher1.
fetcher.threads.fetch = 80
fetcher.threads.per.host = 80
fetcher.server.delay = 0
generate.max.per.host = 1
With a queue size of ~40,000, the result is:
activeThreads=80, spinWaiting=79, fetchQueues.totalSize=0
with maybe a download of 1 page per second.
Runing with -noParse makes little difference.
CPU load average is around 0.2. With Fetcher1 CPU load is around 2.0 - 3.0
Hosts already cached by local caching NS appear to download quickly upon a re-fetch, so possible issue relating to NS lookups, however all things being equal Fetcher1 runs fast without pre-caching hosts.