Tuesday, April 16, 2013

SAN To SAN Replication Failing To Remote DR Site

I had my SAN guy coming to me telling me that there was a problem with the network and that some troubleshooting was in order.  He was getting replication errors from one SAN in our main site to the SAN at the remote site.  I couldn't see any real evidence of a network problem, so I pushed it back on him.  Well, it was a back and forth pushing of responsibility on this issue.  Part of the problem was the terminology he used in describing what a "network" problem was.  He used terms like 'routing problem' in trying to describe to me what his issue was.  A simple ping proved to me there was no routing issue and that his SAN should be able to get to the remote SAN, especially since I could put my laptop on his SAN VLAN range and ping the remote SAN.  No routing problem there. 
However, he did have an issue, and here is what I did in our case to resolve this problem.  I had to do three things, all of which I did without knowing for sure what the real issue was:
1.  I enabled jumbo frames on all switches (I know for sure this did not fix the issue)
2.  I put in on both ASAs the 'fragment chain 1' command
3.  I changed the interface settings on the ASAs (in this case, I had to set it to 'auto' to NOT get errors)

Either #2 or #3 resolved this issue and SAN to SAN replication is working now without issue.  Very interesting problem and we now have resolution to it.

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