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A Short Story

There is an Antminer server farm I provide support for with over 100 BC servers—mainly S9 and T9 models. There are three specific S9 miners that are side by side right next to each other on the rack which continually show lower than normal hash rate in Slushpool.

When I check these servers in Slushpool they all three fluctuate often ranging from 11-13 TH/s but the web interface and command line RT and AVG hash rates are always normal with no fluctuation. Every time I check Slushpool though, it's almost always lower than normal and I've checked up to nearly a hundred times in one day just to ensure I was being thorough.

Question

Is there anything common or something someone else determined that could cause a miner hash rate to always show lower in Slushpool than what it shows from the local server?

Notes

  • I've checked both command line and web interface on all these and see the same thing; normal realtime and normal average always every time I check but with Slushpool, it almost always shows it is hashing lower by 1 or 2 TH/s.

  • Typically when other miners in this farm have a lower than normal Slushpool hash rate, the local servers have a value that correlates much closer to that hash rate so I'm trying to understand if there's something I don't understand here which may explain this.

  • Let me know what further I can provide but there are also other servers in this same area than just those three that don't do this and it's just those three. I've already done several reboots too (web, ssh, and hard boot) and that doesn't help. If it's lower than normal then it is, but I don't understand why SP and local HRs are so far off every time I check and compare. I haven't noticed this with any other servers. – Pimp Juice IT Nov 30 '18 at 5:19
  • When I say the RT and AVG hash rates are always normal with no fluctuation, the local RT and AVG are always 13.5+ TH/s when Slushpool may continually show low 11 or 12's so it seems odd the average on the local miner would still show 13.5+ AVG, unless perhaps there's a bug or something with a specific firmware version, etc. or perhaps something else someone can help me understand which I currently don't. Let me know what further I can provide or troubleshoot regarding this inquiry. – Pimp Juice IT Nov 30 '18 at 5:23
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I believe that whatever is showing up on your dashboard is probably the most accurate picture of hashrate that you're contributing. Because you're mining to a pool, there will inherently be some, slight mismatch.

I wouldn't consider fluctuations a major issue unless it says you're producing far below the advertised hashrate.

I do know that Slushpool uses a "scoring hash rate," and if you want to know how that works in some more depth, here's a link to an article that Slushpool released. Hope this helps!

https://blog.slushpool.com/effective-hash-rate-af9c90529f6d

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Without knowing exactly how Slushpool calculates the hashrate of your miner, it'd be hard to say for sure. But in general mining pools can only take guesses about your hashrate, and it won't be exact. This is done by them sending you blocks to solve (shares) with easier difficulty than what is needed to mine an actual bitcoin block, and seeing how fast you can solve it. Obviously, the speed at which you solve the block will vary so it will not be an accurate way to measure your hashrate in the short term, and you will see a variance.

You have direct access to the machine, which should give you a readout of the hashrate, and naturally this will be different from Slushpool's estimate.

  • Okay, so what the local machine says is accurate then and the pool may not be 100% accurate, correct? You say the pools generally only guess so I would assume that's the case but wanted to ask. – Pimp Juice IT Nov 30 '18 at 12:57
  • pool's guess of the hashrate will not be 100% accurate in the short term. But over the long term, their multiple guesses will average to your actual hash rate unless there is some problem in how they calculate the guess. – kaykurokawa Nov 30 '18 at 16:32

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