On Wed, Mar 09, 2011 at 11:51:20AM -0600, Dimitri Maziuk wrote:
> Dejan Muhamedagic wrote:
> > On Tue, Mar 08, 2011 at 02:27:52PM -0600, Dimitri Maziuk wrote:
> 
> >> Well, realistically, if the link is a foot of x/over cable and gremlins 
> >> have not been pulling on it, and the NICs aren't falling out of their 
> >> slots, and are half-decent quality hardware, and the drivers aren't 
> >> alpha prototype code, and so on, the chances of it being the "link down" 
> >> case should be fairly low.
> > 
> > LOL. BTW, the gremlins I saw doing that were wearing company
> > badges and pulling wrong cables. Realistically, never
> > underestimate human factor :)
> 
> That's why we put locks on our server room doors. So that I am the only 
> gremlin there.

Well, that's good for your cluster too. But it places a bit of
an extra burden on you. I guess that in some shops you'd need to
clone yourself or sth else, otherwise you just wouldn't scale
with demand.

> (Last time I saw split-brain was when I myself pulled on the x/over 
> cable. Really. If you have an rj45 connector with the little tab broken 
> off, throw it out and get a new one now. Trust me, it's much cheaper 
> than the alternative.)

So, did you have stonith in place then? ;-)

> Seriously, though, you have to weigh the cost of ipmi daughterboards or 
> net-connected power strips vs the likelyhood of losing that cross-over 
> link vs the likelyhood of the power strip itself going titsup and taking 
> down your entire cluster. *Then* say "go get a real stonith device".

The cost of decent fencing hardware is nowadays really small.
And the probability of the power supplies going bad is much
higher than that of PDU/PSU. And so on. :)

Cheers,

Dejan

> Dima
> -- 
> Dimitri Maziuk
> Programmer/sysadmin
> BioMagResBank, UW-Madison -- http://www.bmrb.wisc.edu
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