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The formula to calculate the numbers of needed servers is wrong, as you can't have fractional servers. You should use the pigeonhole principle[0] [0]: https://

by Vecr 4y ago

The formula to calculate the numbers of needed servers is wrong, as you can't have fractional servers. You should use the pigeonhole principle[0] [0]: https://en.wikipedia.org/wiki/Pigeonhole_principle https://en.wikipedia.org/wiki/Pigeonhole_principle

sd9 4y ago
The only difference in this case is to take the ceiling. The formula seems fine as an approximation.
nmilo 4y ago
So round it, this is engineering, not math. The safety buffer factor accounts for any rounding errors anyways.
deleted 4y ago
[deleted]
sweettea 4y ago
The formula for number of needed servers seems like a fine approximation; I'm very confused how you could use the pigeonhole principle. Perhaps to say that if you have N servers, one of them has at least total_users/N users? But assuming you have a decent methodology for balancing users across servers, and can rebalance to use a new server when added, this has basically the same effects as the formula given so I'm clearly missing why you pointed this out.
cowthulhu 4y ago
The formula/metric is clearly an approximation?
Dylan16807 4y ago
Use it how? The actual pigeonhole principle would conclude that you have multiple users on at least one server, and nothing else. And anything that calculates individual users is the wrong way to do this math.
tiler2915072 4y ago
As others have pointed out for the authors discussion this fact doesn’t really matter. However what does matter is that the authors probably is not estimating the average correctly partially due to this bug. If they scaled without fixing their excessive string storage, they would probably find their estimate to be off. Even with the fix I’d be surprised if the underlying distribution of data per user is normally distributed.
IncRnd 4y ago
That can obviously be rounded. Nobody will really try to purchase 27% of a server. A different issue is that the formula should include "1+Safety Buffer". Otherwise it needs to be run twice, once with the safety buffer and once without. Even so, I didn't take the formulae on this page to be accurate so much as representational.
- gvx 4y ago
  I assumed the "Safety Buffer" is really more of a "Safety Factor", and is equivalent to 1 + what you or I would call a Safety Buffer.
  - IncRnd 4y ago
    Yep. It's really a non-issue. It's was pretty clear to me that the author knows how to use the formula.
ilyt 4y ago
It relies on common sense, thing that you lack.
Backslasher 4y ago
The real formula we used to order servers was more complex than this, and included regional distribution, requirement peaks etc. I can expand more on that process if this is interesting. However, for the context of this post, this crude approximation suffices IMO

by Vecr 4y ago

sd9 4y ago

The only difference in this case is to take the ceiling. The formula seems fine as an approximation.

nmilo 4y ago

So round it, this is engineering, not math. The safety buffer factor accounts for any rounding errors anyways.

deleted 4y ago

[deleted]

sweettea 4y ago

The formula for number of needed servers seems like a fine approximation; I'm very confused how you could use the pigeonhole principle. Perhaps to say that if you have N servers, one of them has at least total_users/N users? But assuming you have a decent methodology for balancing users across servers, and can rebalance to use a new server when added, this has basically the same effects as the formula given so I'm clearly missing why you pointed this out.

cowthulhu 4y ago

The formula/metric is clearly an approximation?

Dylan16807 4y ago

Use it how? The actual pigeonhole principle would conclude that you have multiple users on at least one server, and nothing else. And anything that calculates individual users is the wrong way to do this math.

tiler2915072 4y ago

As others have pointed out for the authors discussion this fact doesn’t really matter. However what does matter is that the authors probably is not estimating the average correctly partially due to this bug. If they scaled without fixing their excessive string storage, they would probably find their estimate to be off. Even with the fix I’d be surprised if the underlying distribution of data per user is normally distributed.

IncRnd 4y ago

That can obviously be rounded. Nobody will really try to purchase 27% of a server. A different issue is that the formula should include "1+Safety Buffer". Otherwise it needs to be run twice, once with the safety buffer and once without. Even so, I didn't take the formulae on this page to be accurate so much as representational.

gvx 4y ago
I assumed the "Safety Buffer" is really more of a "Safety Factor", and is equivalent to 1 + what you or I would call a Safety Buffer.
- IncRnd 4y ago
  Yep. It's really a non-issue. It's was pretty clear to me that the author knows how to use the formula.

ilyt 4y ago

It relies on common sense, thing that you lack.

Backslasher 4y ago

The real formula we used to order servers was more complex than this, and included regional distribution, requirement peaks etc. I can expand more on that process if this is interesting. However, for the context of this post, this crude approximation suffices IMO