# How to calculate availablity ? 3 Examples

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How is availabilty calculated? After having read some comments I am still

confused.

The best would be if someone could tell me the availability values for the following 3 simple

examples. Assuming that there is a download with (only) 5 chunks/pieces and 2 resp 3 seeds/peers

"y" indicates that the chunk is available.

What would be the availability for:

1.scenario:

chunk No 12345

peer No1 yynnn

peer No2 nnnyy

2.scenario:

chunk No 12345

peer No1 yyynn

peer No2 nnyyy

3.scenario:

chunk No 12345

peer No1 yyynn

peer No2 nnnyy

peer No3 yyyyy

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Total availability (lower graph under General) is you + everyone else.

Availability is the reported availability of peers HAVEs versus NOT HAVEs.

In your examples not including you is an oversight, so I will assume you have nothing (starting @ 0%)

1) .800

2) 1.200

3) 2.000

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Ok, so there is no guarantee that an availibilty > 1.0 indicates that ALL chunks are available (at least once per chunk)?

Is there another way to detect if at last 1 source exist for EVERY chunk?

From what you have said it would mean that:

4.scenario:

chunk No 12345

peer No1 yynnn

peer No2 nnnyy

peer No3 yynyy

peer No4 yynny

has a "huge" availability of 11/5 = 2.2 but could never be successfully finished.

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I'd guess availability is 0.8 since there is no full copy. You'll see red block in the middle of the graphical representation of availability. Also block 4 will show up less blue.

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What this means is there does not need to be a SEED in the swarm as long as between them... your #2 was a prime example of this.

You totally missed the math involved

has a "huge" availability of 11/5 = 2.2 but could never be successfully finished.

It does not have a 11/5 available. That is .800.

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I don't know exactly how it is calculated but I always treat it like the whole number is the number of times the least available piece is available. I pretty much ignore the number behind the comma unless the whole number is 0. Then its a very accurate count of how many % of the pieces ARE available.

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The whole number is the number of complete sets of pieces out there.

If the number is less than 1, there is NO complete set seen.

For each full increment greater than 1, there is a complete set.

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Ok. But you should append "at this moment" !!

If the only seed goes online e.g. only on weekends then the availability

is on working days below (!) 1

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If you do not see total availability > 1.000 you cannot complete the torrent. You must remain in the swarm until such time that condition is met, or stop the torrent and delete the data.

pstein, that's the problem though, with just a torrent file (infohash) you have no other data about the swarm. Unless you are at the client and see a seed connect that one time a week, you may think the swarm is dead. But the fact remains unless you see availability > 1 the swarm cannot complete to make other seeds. (There is one caveat to this, as initial/super seeders appear as a peer with 0.0%... so If you see another peer going up proportionately to your % increase it is in all likelihood a masked seeder)

yea

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Also, if you and the only seeder are both firewalled, you'll NEVER connect to it.

...But if there's enough not-firewalled peers on the torrent, then you should still see the torrent precentage increase (slowly?) over time.

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