Preliminary results of MySQL failure tests (tests conducted by Ruben, Luigi and Dawid)

• MySQL running on two physical machines controlled by Oracle Clusterware:
  • Node crash - relocating service to the surviving node and MySQL crash recovery - MySQL downtime ~1 minute 47 sec. (this time can reach several minutes if longer MySQL crash recovery is required, depends on the transaction rate)
  • If an intervention is required on the host currently running MySQL instance or relocation to the other node is needed - clean MySQL shutdown - MySQL downtime ~42 sec.
• MySQL running on a virtual machine (Oracle VM):
  • If an intervention is required on the physical host running Oracle VM - live migration - No MySQL downtime, drupal sites not affected
  • If the physical host running Oracle VM hangs or crashes - OVM must wait for a timeout and restart the host - MySQL downtime of ~6 minutes (this time can be longer if MySQL crash recovery is required, depends on transaction rate)
• Executing 'FLUSH TABLES WITH READ LOCK;' - during consistent backup phase:
  • Anonymous users were able to access web pages with static content, where as logged-in user had to wait until the lock was released.

-- DawidWojcik - 23-Sep-2011