DNS and Failover

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Revision as of 12:42, 20 June 2012 by Mattison.nescentatgmail (talk | contribs) (Created page with " Goals:   *Provide one way replication to a read only copy of the primary datadryad.org server *Make replication as close to real time as possible *Make failover and f...")

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 Goals:  

  • Provide one way replication to a read only copy of the primary datadryad.org server
  • Make replication as close to real time as possible
  • Make failover and failback automatic


Current situation:

  • Dryad production at NCSU runs rsync every minute of everything in /opt (unless the previous rsync run hasn't finished) to the failover system at Duke
  • The failover system is running Bucardo which provides asynchronous database replication of the dryad_repo database from the primary server at NCSU to the secondary server at Duke
  • Apache is configured on the secondary server at Duke to disallow logins or submission of data.  Users would never see this FQDN, but the secondary site can be reached directly at dryad-dev.nescent.org
  • As member universities of MCNC, Duke and NCSU have access to MCNC's Cisco GSS systems.  These systems are redundant and very reliable.  MCNC has configured the servers for DNS based failover from the primary to the secondary datadryad.org systems.
  1. failover is based on http head requests.  If the webserver returns a 200 status, the primary site is considered up.  If not, the GSS sends new DNS requests to the secondary server until the primary server responds again.  http://www.cisco.com/en/US/docs/app_ntwk_services/data_center_app_services/gss4400series/v1.3/configuration/cli/gslb/guide/Intro.html#wp1119392
  2. I have verified that this works as expected using the datadryad.com domain