What happened to P2Pool?
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2) As block sizes increased, the CPU load on p2pool nodes has increased as well. In order to get reasonable efficiency with p2pool, you now need a fairly fast CPU, like a 3+ GHz Sandy Bridge or faster. Network bandwidth and latency requirements have also increased.
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I disagree with you regarding CPU load based on my own testing using both bare-metal and virtual servers. It has been my observation that a p2pool node's efficiency is most affected by the responsiveness of the attached storage array. I found that my getwork times on a Samsung 850 EVO SSD were about 1/2 of that found on a Western Digital Black HDD and that node efficiency improved over 5% as well.