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High Availability through Virtualization

High Availability through Virtualization. Is RAID enough? Tomas Florian. Florien. Consulting Linux servers Windows workstation interoperability VPNs / Remote access .NET development. Summary. High Availability DRBD Failover Heartbeat Virtualization Xen vs VMWare Xen architecture

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High Availability through Virtualization

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  1. High Availability through Virtualization Is RAID enough? Tomas Florian

  2. Florien • Consulting • Linux servers • Windows workstation interoperability • VPNs / Remote access • .NET development

  3. Summary • High Availability • DRBD • Failover • Heartbeat • Virtualization • Xen vs VMWare • Xen architecture • HA + Virtualization • Questions

  4. High Availability : HA • Linux-ha.org project • Graceful degradation Better than:

  5. Challenges • Replicate data • DRBD Network RAID-1 • Failover • Take over responsibilities from the dead peers • Automatically detect failure • Heartbeat node1 node2

  6. Replicate Data: DRBD • Distributed Replicated Block Device • Network RAID-1 • One active drive (primary) • N spare drives replicated on the network in real-time • In case of primary HD failure, switch to one of the available secondary drives • Mount just like any other block device mount /dev/drbd0 /data

  7. Failover : haresources • node1 running Apache • node2 running qmail • node1 dies … apache dies. Node 2: • Take over primary use of DRBD device • Take over IP • Take over Apache

  8. Detect Failure: heartbeat • Ping through ethernet • Split brain • Ping through serial cable + ethernet • STONITH – Shoot The Other Node In The Head .. node2 is dead .. Time to takeover .. node1 is dead .. Time to takeover node1 node2

  9. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2 Active resources Backup resources

  10. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2 Active resources Backup resources Dead resources

  11. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2 Active resources Backup resources Dead resources

  12. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2 Active resources Backup resources Dead resources

  13. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2 Active resources Backup resources Dead resources

  14. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2 Active resources Backup resources Dead resources

  15. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2 Active resources Backup resources Dead resources

  16. Example Apache Named mysql qmail drbd0 drbd1 drbd0 drbd1 node1 node2 Active resources Backup resources

  17. Summary • High Availability • DRBD • Failover • Heartbeat • Virtualization • Xen vs VMWare • Xen architecture • HA + Virtualization • Questions

  18. Xen • Pronounced ‘Zen’ • Open Source • Run multiple virtual machines on one physical machine • Like VMWare but different (better)

  19. Xen Architecture

  20. Setting up Xen • Install xen software on any Linux • Patch Domain-0 kernel • Boot to the new Domain-0 kernel • Deploy Domain-U virtual machines • Allocate disk • Deploy any distribution with a patched Domain-U kernel • …Or use a distribution that does this for you

  21. Full Virtualization vs Paravirtualization • Paravirtualization • Needs kernel patch • Open source guest OS only (MS will not let you patch Windows kernel) • Full virtualization • Hypervisor implemented with VT CPUs • Windows on Xen possible

  22. VT hardware • Intel • Vanderpool technology • Intel Pentium D • Intel Core Duo • AMD • Pacifica • Check that your BIOS also supports VT

  23. VT support in Xen • 2.0.7 stable as a rock (but no VT) • 3.0.2 unstable (VT… almost) • People regularly report success running Windows guests … • … and crashes • Once v3 becomes stable it will be unstoppable

  24. Summary • High Availability • DRBD • Failover • Heartbeat • Virtualization • Xen vs VMWare • Xen architecture • HA + Virtualization • Questions

  25. No virtualization… MySQL samba named Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2 Active resources Backup resources

  26. …with virtualization Web server Mail server Apache qmail MySQL named named drbd0 drbd1 drbd0 drbd1 node1 node2 Active resources Backup resources

  27. Gains • Whole filesystem protection • / … not just /data • Simplified management • Manage failover for few machines rather than tens of services • No complicated syncing of updates or configuration on the nodes • Security: • If one service is hacked, only one VM is compromised

  28. Pit falls • Performance • Running VMs more resource intensive than running daemons • Watch out for: • Virtual Memory thrashing • DRBD sync speed • HD performance • … going overboard • Don’t forget to backup

  29. Resources • Linux High Availability Project • Linux-ha.org • Xen web site • Google search for “xen” • Xen Distributions • SuSE • FC5 • Xen Live CD • … or just compile on any 2.4.x - 2.6.x kernel • Paid support • www.florien.ca

  30. Summary • High Availability • DRBD • Failover • Heartbeat • Virtualization • Xen vs VMWare • Xen architecture • HA + Virtualization • Questions

  31. Questions

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