Howdy, all.
I'm wondering if any of you have war stories on the topic of tape throughput debugging. I've got some confusing things happening here, and I'm looking for ideas. Take this as a caveat for the long-distance virtual volumes, if you swing that way. :) This is all AIX, for starters. I've measured single stream traffic to my remote site 350 miles away at 60-80MB/s over and over again. Recently, though, I've been seeing several hour periods in which a given stream is limited to 15M/s. Or, it seems that way: 3 streams bobble around in the vicinity or 45M/s, 2 wander around in the vicinity of 30. This is during times when the source machine and the destination machine are both significantly idle, 50% or more. So it's not a gross 'box is busy' thing. It includes periods when I'm sending single large files on all the streams, so it's not database contention for recording the ongoing copies. I can get straight network traffic (iperf) to fill the Gb connection without a problem, so it's not a bottleneck in the intervening net. Unfortunately, that leaves me with the Great Trackless Waste of TSM: tape performance analysis. Ugh. I'm at the spot where I'm considering going Windows and just restarting the things. Ick. - Allen S. Rout
