I think that databases must be kept as a single server. Files are stored on Coda, but
only one DB server is running.
If the machine fails, we first have to check the files on another machine, then start
a new DB server, and redirect all queries to this new server. This isn't High
Availability, but it's still good. Maybe there can be a problem when cheking the files
on another machine, but Coda should take care of all that clearly.
Nicolas Huillard
-----Message d'origine-----
De: Chris Snyder [SMTP:[EMAIL PROTECTED]]
Date: mardi 9 mai 2000 22:04
À: [EMAIL PROTECTED]; [EMAIL PROTECTED]
Objet: Re: High Availability
That seems like it would work, but what happens if there is a lot of data
such as MySQL databases that is tough to combine, if two servers have
different updates after a reconnect?
----- Original Message -----
From: "Jan Harkes" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, May 09, 2000 3:35 PM
Subject: Re: High Availability
> On Tue, May 09, 2000 at 06:46:44PM +0200, Nicolas Huillard wrote:
> > I'm finishing reading Dr Le Blanc's presentation of Coda
> > (http://www.mcc.ac.uk/~zlsiial/coda/text47.html) and also wonders
> > if... (quote :) "Finally, I wonder whether Coda's success as
> > high-availability software is impaired by the dependence of a cell on
> > a single System Control Machine." I am really concerned about this
> > issue, because my goal is to build High Availability...
> > Does anyone have an idea ?
>
> The coda clients and servers do not rely on the existence of an SCM. The
> only reason that machine is special is because of the way we propagate
> updates to the user and volume databases. They are read/write on the
> SCM, and the other servers check for updated files on the SCM once every
> 30 seconds.
>
> If you lose the SCM, all servers can still rely on their local copy. But
> in order to add a volume or user, you need to restore the old SCM. Or
> designate one of the other servers (all of them should have all of the
> required data) as the replacement SCM. To do this is is necessary to
> update the /vice/db/scm file on all servers, and restart the
> updateclnt/updatesrv processes. Not as good as a quorum based replicated
> database server, but a lot simpler for the common case.
>
> Jan
>
application/ms-tnef
