Subject: Re: [vserver] Very serious hashify mysql/innodb conflict causes major data loss
From: Herbert Poetzl <herbert@13thfloor.at>
Date: Sun, 14 Jun 2009 01:03:08 +0200

On Sat, Jun 13, 2009 at 09:58:17PM +0100, Ed W wrote:
> John A. Sullivan III wrote:

> >Thanks! That saved me some serious grief - John

> It would still be very interesting to try and find what's causing the 
> issue though.  The logic of vhashify should only create hard links 
> between identical files.  In fact I'm curious how/why it's even updating 
> directory times?

because in unix creating or removing a file/link is
a directory operation?

> I don't have the logic of the hash open right now, but presumably we 
> need to unlink one side and hard link the otherside (or perhaps it 
> copies/moves one side into the cache folder and hard links everything 
> else?)  The point being I guess if you had an open file which got 
> hardlinked then you might be unlucky enough to end up writing to 
> something which was now unlinked?

that is entirely possible, but quite unlikey, because
chances are small that an open database is identical
to another

> That your writes to the innodb log files have stopped suggests that 
> perhaps part of the log files got linked while open?  However, this 
> seems unlikely given that the data files ought to be completely 
> different in all your vservers?

correct, my guess would be that innodb is being too
smart and deducates something from the fact that
some time stamps for updated

best,
Herbert

> Do you do anything special which might cause these files to look 
> identical before running vhashify?

> Ed W