[elephant-devel] Backend and data retrieval questions

[Red Daly]

On Tue, Oct 21, 2008 at 1:37 PM, Alex Mizrahi <killerstorm at newmail.ru>wrote:

>  RS> First, since I need to use multiple web application machines, I'm
>  RS> using the Postmodern backend. I assume there's no sane way to share a
>  RS> BDB db between multiple machines?
>
> i think so too


Berkeley DB supports "replicated" database environments with many read-only
environments and one environment responsible for all the writing.  (It is
not centralized, however, so when the write-enabled DB goes down it will be
automatically replaced.)  All the data exists on each instance of the
database, so this does not spread the pain of storing tons of data.  There
is also the problem of hitting the write wall since one machine handles all
writing.  Fortunately these problems only affect extremely large
applications.

BDB does not provide any code to handle the networking required to get this
replicated mode working.  You have to write a few functions to do that
yourself (presumably in C unless Lisp can handle FFI callbacks, but I don't
think it can for most lisps).  It should be fairly trivial networking code,
however, and somebody may have already written it out there on the web.

http://www.oracle.com/technology/documentation/berkeley-db/db/ref/cam/intro.html

enjoy elephant :)

-Red
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