Drupal Con My Sql Ha 2008 08 29
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This document discusses high availability solutions for MySQL databases. It covers MySQL replication, MySQL Cluster, and DRBD. MySQL replication allows for one master and multiple slaves but has some limitations. MySQL Cluster provides automatic partitioning and failover between data nodes. DRBD can synchronize block-level replication between nodes for increased availability. The document provides an overview of each technology and their strengths for high availability use cases.
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Drupal Con My Sql Ha 2008 08 29
- 1. High Availability Solutions for MySQL Lenz Grimmer <[email protected]> 2008-08-29 DrupalCon 2008, Szeged, Hungary
- 2. Agenda ● High Availability in General ● MySQL Replication ● MySQL Cluster ● DRBD ● Links/Tools
- 3. Why High Availability Matters ● Downtime is expensive ● You miss $$$ ● Your Boss complains ● New Site visitors won't come back
- 4. What Is HA Clustering? ● One service goes down → others take over its work ● IP address takeover, service takeover ● Not designed for high-performance ● Not designed for high troughput (load balancing)
- 5. Split-Brain ● Communications failures can lead to separated partitions of the cluster ● If those partitions each try and take control of the cluster, then it's called a split-brain condition ● If this happens, then bad things will happen http://linux-ha.org/BadThingsWillHappen ● Use Fencing or Moderatation/Arbitration to avoid it
- 6. Eliminating the SPOF ● Identify what will fail ● Disks ● Find out what can fail ● Network cables ● OOM ● Power supplies
- 7. Rules of High Availability ● Prepare for failure ● Keep it simple, stupid (KISS) ● Complexity is the enemy of reliability ● Test your setup frequently
- 8. MySQL Replication ● One-way, statement-based ● One Master, many Slaves ● Asynchronous – Slaves can lag ● Master maintains binary logs & index ● Easy to set up ● Built into MySQL ● Replication is single-threaded
- 9. MySQL Replication Overview Read & Write Web/App Server Write Relay Log mysqld I/O SQL Thread Thread Index & Binlogs Daten Replication Binlog Data mysqld MySQL Master MySQL Slave
- 10. Replication Topologies Master > Slave Master > Slaves Master > Slave > Slaves Masters > Slave (Multi-Source) Ring (Multi-Master) Master < > Master (Multi-Master)
- 11. Replication & HA ● Combined with Heartbeat ● Virtual IP takeover ● Slave gets promoted to Master ● Side benefits: load balancing & backup ● Tricky to fail back ● No automatic conflict resolution ● Proper failover needs to be scripted
- 12. Master-Master Replication ● Useful for easier failover ● Not suitable for load-balancing ● Writes still end up on both machines ● Neither machine has the authorative data ● Don't write to both masters! ● Use Sharding or Partitioning instead (e.g. MySQL Proxy)
- 13. MySQL Cluster ● Shared nothing ● Automatic partitioning ● Distributed Fragments ● Synchronous replication ● Fast automatic fail-over of data nodes ● Automatic resynchronization ● Transparent to Application ● Supports Transactions
- 14. MySQL Cluster ● In-memory tables ● Not suitable for all query patterns ● Not suitable for large datasets ● Latency matters ● Can be combined with MySQL Replication
- 16. DRBD ● Distributed Replicated Block Device ● “Raid-1 over network” ● Synchronous block replication ● Automatic resync on recover ● Application-agnostic ● Can mask local I/O errors ● Active/passive configuration
- 17. DRBD & Heartbeat ● Heartbeat mounts file system on failover (passive node becomes active) ● Data only accessible on the active node ● (LVM snapshots can work around this) ● Increased I/O Latency ● Failover is “cold” (fsck, log recovery, buffers/caches)
- 18. MySQL Replication & MySQL, Heartbeat & MySQL Requirements MySQL Replication Heartbeat DRBD Cluster Automated IP Failover No Yes Yes No Automated DB Availability Failover No No Yes Yes Typical Failover time Varies Varies < 30s < 3s Auto resync of data No No Yes Yes Geographic MySQL redundancy Yes Yes MySQL Replication Replication Built-in load Scalability balancing MySQL Replication MySQL Replication MySQL Replication Yes Read-intensive Yes Yes MySQL Replication Yes Write-intensive No No Possible Yes #Nodes/Cluster Master/Slave(s) Master/Slave(s) Active/Passive 255
- 19. Related tools / Links ● Linux Heartbeat http://linux-ha.org/ ● DRBD http:/drbd.org/ ● Linux Cluster Information Center http://www.lcic.org/ha.html ● Red Hat Cluster Suite http://www.redhat.com/cluster_suite/ ● Sun Open High Availability Cluster http://opensolaris.org/os/project/ha-mysql/
- 20. Tools/Links ● MySQL Multi-Master Replication Manager http://code.google.com/p/mysql-master-master/ ● Maatkit http://maatkit.sourceforge.net/ ● Mon – scheduler and alert management http://www.kernel.org/software/mon/ ● Continuent Tungsten Replicator https://community.continuent.com/community/tungsten-replicator