Hi Andreas, All the servers have the same /etc/resolv.conf file: search our.domain.com options ndots:2 nameserver ns0IP nameserver ns1IP I can't see any errors on the web servers or nfs servers referring a host lookup failure. Thanks Simone On 8/15/07, Andreas Rogge <arogge at gmx.de> wrote: > > Hi Simone, > > what nameservers are configured for the nfs-servers? > > Afaict the nfs-server does forward and reverse lookup the clients. So if > your nfs-server's DNS breaks (i.e. if only ns0 is configured there and > you shut down ns0) you might see the issue you described. > > Regards, > Andreas > > Simone schrieb: > > Hi all, > > > > Today we have had a strange problem that has taken down our website, we > > understand what happened but not why so I am hoping someone has seen > > this before. > > > > We have our web servers (web1 web2 web3 ..... web10) mounting an NFS > > share (/export/data) from server nfs1. On the web server side we use > > autofs in the format nfs-dedicated:/export/data where nfs-dedicated is > > an alias in our internal DNS servers pointing to server nfs1. We run a > > primary and a secondary DNS (bind) server ns0, ns1 authoritative for our > > zones and our webservers have them configured in /etc/resolv.conf > > Today we had to run some upgrade on the dns servers (bios firmwares etc) > > so we took down ns0 and with it our website went down. > > All the nfs shares disappeared from the web servers (the logs show > > requests to mount/unmount timing out), but at the same time on nfs1 the > > logs show requests (mount and unmount) coming from the web servers and > > no errors. > > > > As soon as ns0 is back up, all gets back to normal. Minutes later we > > take down ns1 for maintenance and it doesn't have any impact on the > > website. > > > > dig @ns0 nfs-web gives exactly the same results on ns0/1 > > > > Back to the office we try to reproduce the same scenario configuring > > iptables on web3 to block traffic to ns0 but the server (web3) keeps > > working fine reverting to ns1 for name resolution (as you would expect). > > > > Has anybody seen this happening before? Any comment/suggestion much > > appreciated. > > > > Thanks > > > > Simone > > > > _______________________________________________ > > CentOS mailing list > > CentOS at centos.org > > http://lists.centos.org/mailman/listinfo/centos > > > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.centos.org/pipermail/centos/attachments/20070815/d1c26db5/attachment-0005.html>