We have a number of servers (application servers, web servers & ftp servers) running red hat 5 that are all virtual. We also have a similar setup that is Windows-based. Yesterday, our infrastructure team needed to shutdown the primary domain controller so they could move the physical server to a new rack. Their assumption was that as soon as the primary domain controller went down, the secondary domain controller would pick up. As soon as the primary domain controller powered down, the Linux-based app servers all slowed to a crawl, to the point that simply trying to log in via ssh took approximately 3 minutes.
Before we could finish troubleshooting the issue, the infrastructure team was able to bring the primary domain controller back on-line.
During the down-time of the primary domain controller, all windows-based servers appeared to be functioning normally.
Our first thought was that the Linux servers didn't have the secondary domain controller listed as a DNS server, but this is not the case. The red hat servers don't tie into any AD functionality, other than using it as a DNS server.
Any thoughts on what else we could check? We're not really Linux sys admins, so I'm not sure if we're missing something pretty basic.