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Re: I lost 7 bdb repositories yesterday!

From: Daniel Berlin <dberlin_at_dberlin.org>
Date: 2005-07-07 16:46:36 CEST

On Mon, 2005-07-04 at 20:52 -0500, Ben Collins-Sussman wrote:
> On Jul 4, 2005, at 8:31 PM, Adrian Hoe wrote:
>
> >
> > But reliability is more then easy integration/setup. We have
> > systems running on MySQL with more than 250 tables and over 7
> > millions tuples and not crashing at all.
>
> Are you aware that mysql uses BerkeleyDB for transacations? :-)

No it doesn't.
It's an optional feature to have BDB tables in mysql
:)

(and btw, i did try it once, and they were very slow. Jab jab jab,
needle needle needle)
>
> Actually, your mysql database probably has crashed many times, but
> you don't notice. That's because the 'mysqld' process is a single
> point of access for all programs; if the database gets inconsistent,
> mysqld stops serving all requests, recovers the database, then things
> move on smoothly.
>
> The big problem between svn and BDB is that we didn't do it this
> way: there's no single 'svnd' mediating all access to the tables and
> keeping guard over database health. That's the model that BerkeleyDB
> expected we'd follow, and we didn't. Instead, we have N diferent
> programs all using the database (via library linkage), and when one
> program wedges the database, all the others sit around and get stuck
> waiting... or error out. Rather than a daemon automatically noticing
> the problem and recovering, a human has to step in and recover things.
>
> So our big mistake here was not realizing how 'brittle' (easy to
> wedge) BDB would be, in the absence of a central daemon.
>
>
>
>
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Received on Thu Jul 7 16:53:39 2005

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