Solving the Mystery of Link Imbalance: A Metastable Failure State at Scale

Re:Solving the Mystery of Link Imbalance: A Metastable Failu... by ngbronson on Wednesday November 26, 2014 @10:49AM (#8662822)

I coded the fix. We considered some options that had a bias away from the slow links, but we thought it was safer to avoid bias completely. It was fine in my tests, but I couldn't prove that biasing toward the faster link in a 2 link setup wouldn't set up an oscillation.

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Re:Solving the Mystery of Link Imbalance: A Metastable Failu... by cperciva on Wednesday November 26, 2014 @11:08AM (#8662928)

I wondered if that was it, but a 1/RTT loading behaviour seems safe enough to me -- after all, that's exactly what TCP does, and you're presumably not seeing any uncontrolled oscillations from that.

I guess it depends how much minimizing the size of your connection pool matters.

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Re:Solving the Mystery of Link Imbalance: A Metastable Failu... by mabbo on Wednesday November 26, 2014 @10:59AM (#8662878)

Great reasoning. Problem: bias isn't balanced, causing complex failure. Solution A: change the bias. Solution B: remove all bias.

One of these options makes things simpler. I'm always in favor of that.

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