[tahoe-dev] How much size if data fragments are sent to each server

Powell Tallen powelltallen at yahoo.com
Tue Oct 9 09:51:00 UTC 2012

Thanks Frederik,
Yes that answers the question as to whether I can adjust N, H and K. If I got you correct, it means I can adjust (set) these parameters in tahoe.cfg. Does that mean I can change these values? If yes what are the minimum/maximum allowable figures (N, H and K).
One question that I asked that is answered but I am not sure of what it means in the maths "........ each share is a third (i.e. 1/K) of the real file". Does that mean that the size of the fragments of data sent to each server is the same (equal to 1 third of the whole file?)? Can I send different (unequal eg half, 1 fourth, 1 third, etc) sizes of fragments of the data to each server?

From: Frederik Braun <Frederik.Braun+tahoe at ruhr-uni-bochum.de>
To: Powell Tallen <powelltallen at yahoo.com>; Tahoe-LAFS development <tahoe-dev at tahoe-lafs.org> 
Sent: Tuesday, 9 October 2012, 11:10
Subject: Re: [tahoe-dev] How much size if data fragments are sent to each server

Hey Powell,

the amount of shares (needed, happy, total) can be set in your tahoe.cfg.

For this example, let's assume we use N=10, H=7, K=3.

Whenever a file is uploaded, it is encrypted and the cipher text is then
split into 10 shares so that 3 of them suffice for reconstruction, this
means that each share is a third (i.e. 1/K) of the real file. The total
space used on the grid is 10 * (size)/3 (i.e. N * (size)/K) then.
Tahoe tries to upload 10 shares to the grid and will return an error if
less than 7 can be placed.

I hope this answers your question. You might also take a look at the
docs at tahoe-lafs.org

This was just from the top of my head. Correct me if I'm wrong, rest of
the list :)


On 10/09/2012 08:56 AM, Powell Tallen wrote:
> Dear All, Please how much of the fragment of data sent to tahoe grid
> are sent to each server. Is the data divided equally and the sent to
> each server or you can have different sizes sent to each server. I
> also understand that there are N=10 shares, H=7 servers which the 10
> are divided and sent to, and K=3 servers that are needed to
> reconstruct the data in case of any failure. Are these numbers just
> the defaults or one can change the numbers depending on what you
> want. Regards Powell
> _______________________________________________ tahoe-dev mailing
> list tahoe-dev at tahoe-lafs.org 
> https://tahoe-lafs.org/cgi-bin/mailman/listinfo/tahoe-dev
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