high-availability again

Dave McMurtrie dgm+ at pitt.edu
Thu Apr 14 10:47:10 EDT 2005

Amos wrote:

> What sort of changes did you have to make?

We just had to change map_refresh() to call mmap() with MAP_PRIVATE 
instead of MAP_SHARED.  Since mmap() is being called with PROT_READ 
anyway, this doesn't affect the operation of the application since the 
mapped region can never be updated.  Veritas CFS was not very efficient 
about maintaining cache coherency across all cluster nodes when we were 
using MAP_SHARED.  Everything worked, but under heavy load it became 
extremely slow.

> We're planning on doing something similar with Sun Cluster. Why Sun 
> Cluster? Well, it's the only cluster environment that WebCT supports, 
> and managing two completely different clustering technologies would be a 
> bit much for our little brains. ;-)

The folks who ran the upgrade project here tested both Sun Cluster and 
Veritas Cluster.  They chose Veritas Cluster.  We have a few other 
systems here running Sun Cluster (not related to our cyrus 
installation).  Personally, I haven't been overwhelming impressed by Sun 
Cluster and I really like Veritas Cluster.  I have to admit that I try 
to avoid the systems here that have Sun Cluster on them, so my opinion 
might be unfairly biased.  I can also say that we received unmatched 
technical support from Veritas when we did encounter problems.


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