Hosting and dedicated servers: answer questions. Part 4

In this series of articles, we want to consider the issues that people have when working with hosting providers and dedicated servers in particular. Most of the discussions we conducted in English forums, trying to help users primarily with advice and not self-promotion, giving the most detailed and impartial answer, because our experience in the field has been over 14 years, hundreds of successful solutions and thousands of satisfied customers. Nevertheless, our answers should not be perceived as the only correct answers of the first instance, they may well contain inaccuracies and even errors, no one is perfect. We will be grateful if you add or correct them in the comments.

Hosting and dedicated servers: answer questions. Part 1
Hosting and dedicated servers: answer questions. Part 2. Why such an expensive Internet in the data center?
Hosting and dedicated servers: answer questions. Part 3

Why is the cost of a server with a traffic limit of 100 TB and a 1 Gbit / s channel much less than the cost of a server with a 1 Gbit / s channel without considering traffic? After all, if you rent 2-3 servers with a 1 Gbps channel and a limit of 100 TB, you can consume exactly the same amount as would be consumed by a server with 1 Gbps Unmetered, or even more channel in peaks, while the provider provides essentially more iron, more connections and lower price?

The fact is that providers, offering servers with a sufficiently large traffic limit or even “unlimited” for little money, take into account the average consumption profiles of their customers. It turned out that most customers who buy such channels do not fully use the connectivity provided to them. It is thanks to this that it becomes possible to make such an offer.

100 TB of traffic is a pretty big limit. This is more than 100 Mbps Unmetered. After all, having a channel of 100 Mbit / s without accounting, you can pump a maximum of 100 (speed in megabytes) * 86400 (number of seconds in days) * 30 (days) / 8 (bits in bytes) / 1000 (megabytes in gigabytes, if we count 1000, and not 1024, 1024 – this is a bit in kibibit) = 32,400 GB per month in each direction with constant download of the channel at 100%. However, as we know, servers do not consume traffic constantly and very often daily consumption curves can look like this:

Someone peaks can reach maximum throughput and require an honest 1 Gb / s at these times. Moreover, the total traffic limit per month can be almost not exceeded:

Such clients, of course, are not very beneficial to providers, and therefore the provider wants to transfer them to Unmetered, because if he provides services to customers from one region, it is likely that the consumption peaks will coincide and this “honest” gigabit provider can only sell 1.2 customer. If the provider has customers from different regions, then it is likely that the channel can be sold to two or more subscribers at once, since the peak consumption of audiences will occur at different times. In reality, by no means every client consumes its own limit of 100 TB; therefore, providing servers with a limit of 100 TB of traffic is extremely beneficial.

Moreover, connecting 10 gigabit channels to the racks, it is possible to very effectively share traffic between everyone. We manage to divide the 10 Gb / s channel on average into 5 racks filled with servers with a limit of 100 TB. These are approximately 150 servers. Since one rack with a height of 47 units can accommodate either 41 single-server servers or 21 two-unit servers.

As a result, the total channel consumption is as follows:

If you refuse to provide services to subscribers who generate a lot of traffic (less than 10 out of 150 servers present on this port make the main contribution to channel loading), then you can increase the number of servers to 300 or more. And everyone will be happy and everyone will have enough traffic.

However, there are other ways to save money and not upset subscribers – connect a cheaper transit uplink or send traffic to an exchange point or peering for free if you are a large traffic generator.

This is all that allows you to provide low prices, not to refuse service to subscribers, paying transit providers 1,500-6,000 euros for every 10G, depending on how good a transit provider is and selling connectivity is cheaper than the cost with a certain oversell ratio, when each of the subscribers has its own ordered an honest channel, while not interfering with each other.

It immediately becomes clear why the price of 1Gbps Unmetered is much higher, since if with 100 terabyte servers, not everyone consumes their limit, then the client who orders 1Gbps Unmetered will clearly consume most of the channel. Although we saw the above exception and an example of how you can generate almost 1 Gbit / s of traffic at the peaks and still be within the 100 terabyte limit, but this is an exception, not a typical pattern.

My administrator installed the vnstatd program on the server, the traffic is removed from the interface, it is removed every 5 minutes. Does he take everything into account? So it shows me that 87 TB are used, while the provider says that 96 TB is used and the traffic is almost over. I am confident in my system administrator, this is an excellent specialist. And if he says that the provider inflates the expense – it is. Moreover, this is indicated by the fact that they began to play with might and main with values ​​giving in the process of discussion different values ​​for traffic for the same period. To the question “how so?” we are still waiting for an answer.

The fact is that some traffic accounting programs keep records in TiB, not TB. Terabytes, not terabytes. That is, the accounting is carried out according to the binary system, and not the decimal, based on the fact that in kilobytes, or rather in kibibytes – 1024 bytes, not 1000.

It is worth noting that in order to prevent this distinction from being used for marketing purposes, ISO (International Standartization Organization) has long introduced binary prefixes for binary bytes, that is, kibibytes, mebibytes, gibytes, terabytes. That’s just, marketing still took place, and if drive manufacturers, due to decimal bytes, manage to indicate lower drive capacities, then the situation is opposite when measuring and accounting for traffic. The hosting provider, providing 100 TB of traffic, provides it less than it can actually be, if you take it into account on a binary system.

It would seem that the difference is small, only 24 bytes per 1000, the error from this is only 2.4%, but why is there such a big difference at the level of 10%? Maybe they really didn’t take into account any traffic?

The fact is that we must not forget that the “error” is growing, namely:

1024 bytes in kibibyte (if we speak in accordance with ISO standards), in mebibyte already 1024 * 1024 = 1,048,576 bytes, in gibyte – 1,024 * 1,024 * 1,024 = 1,073,741,824, and in tebibyte – 1,024 * 1,024 * 1,024 * 1024 = 1,099,511,627,776.

Unexpected turn? Yes?

When measuring traffic in terabytes, the difference between accounting units is exactly 10%!

Moreover, the difference in the data taken from the port of the switch and from the port of the server can be caused by a DDOS attack, which does not reach the client, and can be eliminated at the “router” level, while traffic consumption still occurs.

You should also not forget that sometimes, the program does not take into account traffic on all ports, and some traffic may “slip away” from monitoring.

It also follows that when limited traffic is provided, the total incoming + outgoing is often taken into account, and if you have, say, a VPN service, the ratio will be 1 to 1 and your customers will be able to pump a total of no more than 50 TB of traffic with a limit of 100.

To be continued…

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