[Info-vax] Distant Cluster?

[Christoph Gartmann]

In article <k4pl2v$kks$1 at dont-email.me>, Stephen Hoffman <seaohveh at hoffmanlabs.invalid> writes:

>You mention "distant" in the title.  How distant?  The 
>officially-supported cluster distance is 500 miles / 800 kilometers 
>with the HP default cluster configuration support.  Longer spans can 
>and do work, though you'll (officially) want to work with HP if you 
>need formal support.

Approximately 500 meters, still within the same LAN.

>> Now it is possible to shutdown all the Alphas, the Itanium boxes continue to
>> run and vice versa. But if the network connection between the two sites drops,
>> the Itaniums crash. Why?
>
>Because you haven't yet configured a stable network, or haven't added a 
>parallel/redundant connection?  Or because your network is getting 
>overloaded, and  the load of (for instance) shadowing is saturating the 
>wire?  Or wasn't that the (intended) question?

There are a few switches between the two locations. These need software updates
from time to time and require a reboot...

>FWIW, the hosts usually crash when the network connection resumes, 
>because they're determined to the "outliers" in the cluster and 
>CLUEXIT; you ended up with a partition, and the Alpha boxes "won" the 
>decision during the reconnection process.
>
>Why does this happen?  Partitioning.  Or more specifically, avoiding 
>partitioning.

Ok, I understand.

>The ugly approach is to increase the cluster timeout past your 
>networking group's typical network outage interval; see RECNXINTERVAL 
>here 
><http://h71000.www7.hp.com/doc/84final/4477/4477pro_026.html#clus_sysgen> 

A switch requires 2 minutes to reboot. So I think this is a bit too long.
I will think about alternate network paths.

Regards,
   Christoph Gartmann

-- 
 Max-Planck-Institut fuer      Phone   : +49-761-5108-464   Fax: -80464
 Immunbiologie und Epigenetik
 Postfach 1169                 Internet: gartmann at immunbio dot mpg dot de
 D-79011  Freiburg, Germany
               http://www.immunbio.mpg.de/home/menue.html