[Gluster-devel] solutions for split brain situation

[Steve]

-------- Original-Nachricht --------
> Datum: Mon, 14 Sep 2009 21:14:32 +0200
> Von: Stephan von Krawczynski <skraw at ithnet.com>
> An: Anand Avati <avati at gluster.com>
> CC: gluster-devel at nongnu.org
> Betreff: Re: [Gluster-devel] solutions for split brain situation

> On Mon, 14 Sep 2009 21:44:12 +0530
> Anand Avati <avati at gluster.com> wrote:
> 
> > > Our "split brain" is no real split brain and looks like this: Logfiles
> are
> > > written every 5 mins. If you add a secondary server that has 14 days
> old
> > > logfiles on it you notice that about half of your data vanishes while
> not
> > > successful self heal is performed, because the old logfiles read from
> the
> > > secondary server overwrite the new logfiles on your primary while new
> data is
> > > added to them.
> > 
> > Have you been using favorite-child option? 
> 
> No, the option was not used.
> 
> > Auto resolving of
> > split-brain is bound to make you lose data of one of the subvolumes.
> > If you had indeed specified favorite-child option, and the
> > favorite-child option happens to be the server which had 14day old
> > logs, what just happened was exactly what was in the elaborate warning
> > log.
> > 
> > Now what is more interesting for me is, the sequence of taking down
> > and bringing up the servers you followed to split brain? Was is really
> > just taking one server (any of them) down and bringing it back up? Did
> > you face a split brain with just this? Can you please describe the
> > minimal steps necessary to reproduce your issue?
> 
> Take 2 servers and one client. Use a minimal replicate setup but do _not_
> add
> the second server. Copy some data on the first server via glusterfs, then
> rsync that data on the second server directly from the first server
> (glusterfsd not yet active there). Now change some of the data to have
> files
> that are really newer as your rsync cycle. Then start glusterfsd on the
> second
> server. Your client will add it. Then open the newer files r/w on the
> client.
> You will notice the split brain messages in the client logs and find that
> every
> other file gets indeed read in from the second (outdated) server fileset.
> Write it back and your newer files on the first server are gone.
> As said, no favorite child option set.
>  
You just rsynced but did you synced the extended attributes as well?


> > Avati
> 
> -- 
> Regards,
> Stephan
> 
> 
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