[tahoe-dev] "servers of happiness" Re: MapReduce over Tahoe-LAFS slides from HadoopWorld
zooko at zooko.com
Tue Oct 13 13:23:49 UTC 2009
I asked my wife Amber for help formalizing my intuition about what
sort of share placement makes me happy. We came up with this:
First of all, let's call a set of servers "sufficient" if you can
download the file from that set (i.e. if at least K distinct shares
are hosted in that set of servers).
Now consider the largest set of servers such that every K-sized
subset of it is sufficient.
Let's call the size of that largest set S. Now my intuition about
"Happyness" is that I configure a Happyness number H, and if an
upload results in an S >= H then I'm happy.
I think this is also Robert Metcalf's intuition . It may also be
Shawn Willden's intuition , but on the other hand perhaps Shawn
Willden's intuition is something more sophisticated. ;-)
A neat thing about this way of thinking is that the number S is the
"health" or "robustness" of the file. An upload or a file-check
operation could report S to the user.
What do you think -- is this measure of "health" a good enough
measure for the purposes of ticket #778?
http://allmydata.org/trac/tahoe/ticket/778 # "shares of happiness" is
the wrong measure; "servers of happiness" is better
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