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Atlas standby database tests February 2011

Atlas standby database tests February 2011. Marcin Blaszczyk, IT-DB marcin.blaszczyk@cern.ch. Outline. Standby databases for ATLAS Failover and Switchover Test of standby switchover – February 17 th 2011 Conclusions. Standby databases for ATLAS.

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Atlas standby database tests February 2011

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  1. Atlas standby database testsFebruary 2011 Marcin Blaszczyk, IT-DB marcin.blaszczyk@cern.ch

  2. Outline • Standby databases for ATLAS • Failover and Switchover • Test of standby switchover – February 17th2011 • Conclusions

  3. Standby databases for ATLAS Standby database is a copy of production database that can be used for disaster protection Dedicated physical standby database for: ATONR database ATLR database ADCR database Read / Write Access Primary database standby database Redo Transport

  4. Standby databases for ATLAS All ATLAS standby databases: Installed on new hardware provisioned in 2010 Quadcore servers and high-capacity disks This has increased resources on standby DBs comparing to previous standby setups Provided good compromise cost/performance in case of switchover operation Are located in Safehostoutside CERN campus Reduce risk in case of disaster recovery Asynchronous transport mode (no influence on primary database performance)

  5. Failover(unscheduled – DB failure) Read / Write Access Read / Write Access Primary database standby database Redo Transport

  6. Switchover (scheduled) Read / Write Access Read / Write Access Primary database standby database Redo Transport Redo Transport

  7. Why failover? Advantages: Failover minimizes downtime –it’s faster than full database recovery from backups no reconfiguration is needed for users and applications Real life scenarios from other LHC experiments: LHCB online database failover August 2010 Reason: power cut in LHCb pit CMS offline database failover March 2011 Reason: Electrical issue with storages in CC

  8. Switchover tests Scenario Tests performed on ATONR cluster to validate disaster recovery scenario and infrastructure Coordinated by Luca Canali (IT-DB),Gancho Dimitrov, Florbela Tique Aires Viegas (ATLAS), Rainer Bartoldus (ATLAS Online DB coordinator) Performed during technical stop on 17th of February 2011 First phase: Standby has been opened in read only mode for testing while primary database was running Several tests performed regarding connectivity checks for online systems Second phase Full switchover All applications have been sucessfully reconnected do primary database while working on standby hardware Switch back to original hardware

  9. Switchover tests General outcome: Tests were successful, switchover scenario has been tested and validated Standby database has been working fine handling production load for around 2 hours after switchover. We are able to do switchover / failover in ~30 minutes Issues encountered during test: DNS local caching can caused some client-specific connectivity problems RDB manager restart solves this problem connection problems encountered for COOL & CORAL reconnecting after switch back to original hardware We believe this was a one-off issue Fixed with a service restart in that particular occurrence

  10. Conclusions In case of Primary database lost: It’s feasible to perform a failover in around 30 minutes Determining that failover is the only and best option can be time consuming Due to asynchronous transport mode transactionlost is possible but limited to seconds No reconfiguration on client side is needed Full database access is guaranteed immediately after switchover Global connection descriptors use aliases instead of physical machine names – all changes on DNS level DNS local caching can cause some client-specific connectivity problems, connection checks needed after of Failover / Switchover

  11. Acknowledgements Luca Canali (IT-DB) http://phydb.web.cern.ch/phydb/

  12. Q&A Thank You! Questions? phydb.support@cern.ch marcin.blaszczyk@cern.ch luca.canali@cern.ch

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