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HA options Cross Site Mirroring (XSM) and Orion

HA options Cross Site Mirroring (XSM) and Orion. Jonathan Woods. XSM - Overview. New ‘Page level’ replication option Native to OS/400 Ultimate protection iASP to iASP via LAN/WAN Sync and Async options High bandwidth Another ‘comms’ option for an HA solution. High level XSM Schematic.

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HA options Cross Site Mirroring (XSM) and Orion

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  1. HA optionsCross Site Mirroring (XSM) and Orion Jonathan Woods

  2. XSM - Overview • New ‘Page level’ replication option • Native to OS/400 • Ultimate protection • iASP to iASP via LAN/WAN • Sync and Async options • High bandwidth • Another ‘comms’ option for an HA solution

  3. High level XSM Schematic Clustering heartbeat High bandwidth WAN • *SYSBAS not replicated • Clustering required to switch device resource group • Orion manages clustering XSM Replication Orion Replication *SYSBAS iASP iASP *SYSBAS

  4. XSM - detail • Initial synchronisation goes via LAN/WAN • Could be lengthy for big disk • 3.5hrs for 100GB over 100Mbps • If communications fail a full re-sync is required for target disk • User operations can continue • Timeout after comms failure can be set • After timeout replication suspended • Sync option also needs high bandwidth to keep source response times good • Async can help relieve this problem

  5. Sync versus Async • Synchronous replication • Target system has to acknowledge disk write back to source system before source app continues • Asynchronous replication • Source system application continues regardless off target disk write • Either source or target transaction queue is required

  6. Clustering Failure Detection, Auto Failover Clustering Failure Detection, Auto Failover Continuous Availability Application users unaffected High Availability Fast manual recovery Application Resilience Application Failover Data Availability Copy of data not application Data Resiliency Data Replication Disaster Recovery Protection from data loss (in case of memory crash) Transaction Integrity Journaling Hardware Protection Raid 5 and Disk Mirroring Data Resilience Physical disk protection The Availability Building Blocks

  7. HA comms options summary • Switched HSL bus disk (local HA only) • OS/400 Remote journaling – sync or async • Orion replication (from journal) – async + reduced bandwidth • Switched disk replication async or sync (ESS-Shark) • XSM replication – async or sync

  8. OS/400 internals Users Proximity to App 1. Main storage is closest 2. OS/400 Journaling 3. Disk subsystem Application Main storage XSM Replication Orion/Remote JRN Replication *FILE PF *JRN ESS/Shark Replication Disk

  9. Conclusion - pure iSeries • If Synchronous replication required, XSM is the best choice there is • If lower cost of async is attractive then Journal based replication has more benefits: • Suspend/resume with no re-sync • Initial Sync via tape could be quicker • Easy backup off target option • Orion relevant either way • Replicates *SYSBAS • Manages clustering

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