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architecture.txt: small edits

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Zooko O'Whielacronx 2007-08-08 22:31:05 -07:00
parent 524c9f1fc2
commit fedab34f83
1 changed files with 7 additions and 9 deletions
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docs/architecture.txt
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@ -24,7 +24,7 @@ Allmydata uses this for a backup service, in which the application copies the
files to be backed up from the local disk into the virtual drive on a
periodic basis. By providing read-only access to the same virtual drive
later, a user can recover older versions of their files. Other sorts of
applications can run on top of the virtual drive, of course, anything that
applications can run on top of the virtual drive, of course -- anything that
has a use for a secure, robust, distributed filestore.
Note: some of the description below indicates design targets rather than
@ -71,8 +71,7 @@ connectivity to participate. In the current release, nodes behind NAT boxes
will connect to all nodes that they can open connections to, but they cannot
open connections to other nodes behind NAT boxes. Therefore, the more nodes
there are behind NAT boxes the less the topology resembles the intended
fully-connected mesh topology. (See also
http://allmydata.org/trac/tahoe/ticket/22 ).
fully-connected mesh topology.
FILE ENCODING
@ -84,12 +83,11 @@ segments so it can be processed in small pieces (to minimize the memory
footprint of both encode and decode operations, and to increase the so-called
"alacrity": how quickly can the download operation provide validated data to
the user, basically the lag between hitting "play" and the movie actually
starting). Each segment is erasure coded, which creates encoded blocks that
are larger than the input segment, such that only a subset of the output
blocks are required to reconstruct the segment. These blocks are then
combined into "shares", such that a subset of the shares can be used to
reconstruct the whole file. The shares are then deposited in StorageServers
in other peers.
starting). Each segment is erasure coded, which creates encoded blocks such
that only a subset of them are required to reconstruct the segment. These
blocks are then combined into "shares", such that a subset of the shares can
be used to reconstruct the whole file. The shares are then deposited in
StorageServers in other peers.
A tagged hash of the encryption key is used to form the "storage index",
which is used for both peer selection (described below) and to index shares