Harald Schmalzbauer schrieb am 17.02.2010 20:15 (localtime): ...
Now my first idea is to compare MSS and windows sizes before and after the performance drop. How do I best capture them? tdpcump? It's GbE linkspeed...It seems more likely that ZFS is running into slowdowns from resource contention, memory fragmentation, etc than your network would suddenly drop out, but tcpdump -w outfile.pcap is a good method of looking....Thanks, but fisrt tests showed that ZFS is not causing the slowdown.
Hello,I got exactly the same limitations when using tmpfs. So for now I'll concentrate on that, back to ZFS later.
Please clarify my TCP understanding.If I have the window set to 65535 in the header and a MSS of 1460, how often should the receiver send ACK segments? window/MSS, right? Now I see every two segments acknowledged in my dump (rsync between two em0 interaces).
I'd like to understanda) why disabling net.inet.tcp.rfc1323 gives slightly better rsync throughput than enabled
b) why I can't transfer more than 50MB/s over my direct linked GbE boxes.But right now I even don't understand the dump I see. As far as I understand I should only see every 45 data segments one ACK segment. That would clearly explain to me why I can't saturate my GbE link. But I can't imagine this is a uncovered faulty behaviour, so I guess I haven't understood TCP.
Please help. Thanks in advance, -Harry
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