docs/about.rst: correct the description of availability to take into account that shares may not be stored on distinct servers.

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david-sarah 2011-10-25 06:25:50 -07:00
parent 633641174a
commit f8be1f6220

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@ -50,10 +50,11 @@ integrity-checked by the gateway, so that the servers can neither read nor
modify the contents of the files.
Users do rely on storage servers for *availability*. The ciphertext is
erasure-coded and distributed across ``N`` storage servers (the default value
for ``N`` is 10) so that it can be recovered from any ``K`` of these servers
(the default value of ``K`` is 3). Therefore only the simultaneous failure
of ``N-K+1`` (with the defaults, 8) servers can make the data unavailable.
erasure-coded into ``N`` shares distributed across at least ``H`` distinct
storage servers (the default value for ``N`` is 10 and for ``H`` is 7) so
that it can be recovered from any ``K`` of these servers (the default
value of ``K`` is 3). Therefore only the failure of ``H-K+1`` (with the
defaults, 5) servers can make the data unavailable.
In the typical deployment mode each user runs her own gateway on her own
machine. This way she relies on her own machine for the confidentiality and