Subject: Re: [vserver] Very serious hashify mysql/innodb conflict causes major data loss
From: Ed W <lists@wildgooses.com>
Date: Sat, 13 Jun 2009 21:58:17 +0100

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?

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 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?

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

Ed W