Hot Diggety! Richard Sims was rumored to have written: > > I would start with the netstat inspection outlined in the "Backup > performance" topic of ADSM QuickFacts, which will quickly assess how > network flow is doing in the actual event. TCP window size may be > involved in what you are seeing, known to be a particular factor over > long distance communication.
I regularly push up to 980 Mbps sustained over a nearly 3,600 mile (~5800 km) WAN, but usually about 175-200 Mbps for a typical workload. Richard is correct: TCP window size tuning is *vital* for a high bandwidth WAN. Don't leave home without it correctly tuned. :-) For instance, according to Sun support working one of our cases, Solaris is tuned for LAN performance out of the box. It's not a lot more to tune it for a WAN, but it does require some careful notes, theory, measurement, and trial-and-error. We also got a major boost in performance merely by enabling jumbo frames on each end. A smaller boost from using certain tunables to push the NICs to their absolute maximum on Solaris. I haven't done AIX perf tuning in so long that I'm a little rusty now, alas. But for AIX, one tunes sliding windows by adjusting these 'no' options: - tcp_sendspace - tcp_recvspace There's a few more 'no' options... rfc1323 is another key one to enable. http://www.performancewiki.com/aix-tuning.html Regardless of the sliding windows values chosen, strongly suggest testing and retesting with various (power-of-2) values until the optimal value is seen. E.g. 1024, 2048, ..., 65536, etc. Also, the original poster may want to check with the network folks (and/or upstream provider if appropriate) to make sure there's no particular segment along the end-to-end network path that is of small bandwidth. In my case, it's all 'in-house' so that makes it easier. E.g. you're not going to see gigabit performance end-to-end if you have, say, a DS3 (45 Mbps) circuit somewhere in between. Also, before making changes, record before/after values as well as results of measurements. Nothing worse than getting muddled in the perf tuning process due to lack of careful record-keeping. Some food for thought. -Dan