MySQL High Availability Solutions
1 like13 views
This document discusses various high availability solutions for MySQL databases. It begins with an overview of high availability concepts and considerations. It then summarizes MySQL replication, disk replication using DRBD, shared storage, and MySQL Cluster. Other high availability tools mentioned include Pacemaker, Galera replication, MMM, Tungsten Replicator, Red Hat Cluster Suite, Solaris Cluster, and Flipper. The document provides information on how these different techniques can be used to add redundancy and eliminate single points of failure for MySQL databases.
MySQL High Availability Solutions
- 1. MySQL High Availability Solutions Lenz Grimmer <lenz@grimmer.com> < http://lenzg.net/ | Twitter: @lenzgr 2011-01-26 | San Francisco MySQL Meetup | USA
- 2. $ whoami 1998 2002 2008 2010
- 3. Agenda ● High Availability: Concepts & Considerations ● MySQL Replication ● DRBD / Pacemaker ● MySQL Cluster ● Other HA tools/applications
- 4. Single MySQL Server MySQL Client SQL (SELECT, INSERT, UPDATE, DELETE) MySQL Storage Engines (InnoDB, MyISAM, PBXT...) Disk Storage (XFS, ReiserFS, JFS, ext3...)
- 5. Why HA? ● Something can and will fail ● Service Maintenance ● Downtime is expensive ● Adding HA to an existing system is complex
- 6. Elimination of the SPOF ● Identify what will fail eventually ● Hard disks ● Fans ● Consider what might fail ● Application crashes ● OOM-Situations, Kernel-Panics ● Network connections, Cables ● Power supply
- 7. What is HA Clustering? ● Redundancy ● One system or service goes down → others take over ● IP address takeover, service takeover ● Ensuring data availability & integrity ● Not designed for high-performance
- 9. Rules of High Availability ● Prepare for failure ● Aim to ensure that no important data is lost ● Keep it simple, stupid (KISS) ● Complexity is the enemy of reliability ● Automate it ● Test your setup frequently!
- 10. HA Components ● Heartbeat ● Checks that services that are monitored, are alive. ● Can check individual servers, software services, networking etc. ● HA Monitor ● Configuration of the services ● Ensures proper shutdown and startup ● Allows manual control ● Shared storage / Replication
- 11. 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 ● Use Fencing or Moderation/Arbitration to avoid it
- 12. Redundancy Using MySQL Replication MySQL Replication
- 13. MySQL Replication ● Unidirectional ● Statement- or row-based (MySQL 5.1) ● Built into MySQL ● Easy to use and set up ● One Master, many Slaves ● Asynchronous – Slaves can lag behind ● New in MySQL 5.5: Semisync Replication
- 14. MySQL Replication (2) ● Master maintains Binary logs & index ● Replication on Slave is single-threaded http://forge.mysql.com/wiki/ReplicationFeatures/ParallelSlave ● No automated fail-over ● No heartbeat, no monitoring ● New in 5.5: replication heartbeat
- 15. MySQL Replication - Overview Read & Write Web/App Server Write Relay Log mysqld SQL I/O Threa Thread d Index & Binlogs Data Replication Binlog Data mysqld MySQL Master MySQL Slave
- 16. Statement-based Replication ● Pro ✔ Proven (around since MySQL 3.23) ✔ Smaller log files ✔ Auditing of actual SQL statements ✔ No primary key requirement for replicated tables ● Con ✗ Non-deterministic functions and UDFs ✗ LOAD_FILE(), UUID(), CURRENT_USER(), FOUND_ROWS() (but RAND() and NOW() work)
- 17. Row-based Replication ● Pro ✔ All changes can be replicated ✔ Similar technology used by other RDBMSes ✔ Fewer locks required for some INSERT, UPDATE or DELETE statements ● Con ✗ More data to be logged ✗ Log file size increases (backup/restore implications) ✗ Replicated tables require explicit primary keys ✗ Possible different result sets on bulk INSERTs
- 18. Replication Topologies Master > Slave Master > Slaves Master > Slave > Slaves Masters > Slave (Multi-Source) Ring (Multi-Master) Master < > Master (Multi-Master)
- 19. Master-Master Replication ● Two nodes are both master and slave to each other ● Useful for easier failover ● Not suitable for (write) load-balancing ● Don't write to both masters simultaneously! ● Use Sharding or Partitioning instead (e.g. MySQL Proxy)
- 20. MySQL Replication as a HA Solution ● What happens if the Master fails? ● What happens if the Slave fails? ● This doesn’t sound like High Availability! ● Yes! ● Replication is only part of a HA configuration
- 21. Pacemaker (Linux-HA) ● Supports 2 or more Nodes (v2) ● Resource monitoring (Apps and HW) ● Active fencing mechanism (STONITH) ● Node failure detection in seconds ● Supports many applications (incl. MySQL) ● http://clusterlabs.org/ ● http://www.clusterlabs.org/wiki/Load_Balanced_MySQL_Replicated_Cluster ● http://www.clusterlabs.org/wiki/DRBD_MySQL_HowTo
- 22. Replication & HA ● Combined with Pacemaker ● Virtual IP takeover ● Slave gets promoted to Master ● Side benefits: load balancing & backup ● Can be tricky to fail back ● No automatic conflict resolution ● Proper failover needs to be scripted
- 23. Redundancy With Disk Replication Disk Replication
- 24. DRBD ● Distributed Replicated Block Device ● “RAID-1 over network” ● Synchronous/asynchronous block replication ● Automatic resynchronisation ● Application-agnostic ● Can mask local I/O-Errors ● Active/passive configuration ● Dual-primary mode (requires cluster file sytem like GFS or OCFS2) ● http://drbd.org/
- 25. DRBD in Detail ● DRBD replicates data blocks between to block devices ● DRBD can be combined with Linux-HA and other HA solutions ● MySQL runs normally Applications on primary node ● MySQL is not active on Active Node Virtual IP Passive Node the secondary node ● DRBD is Linux only DRBD
- 26. Redundancy Using Shared Storage
- 27. Replication vs. SAN ● Data Consistency / Integrity ● Synchronous vs. asynchronous ● SAN can become the SPOF ● Cold caches ● “Split brain”-Situations ● SAN/NAS I/O Overhead
- 28. Redundancy with MySQL Cluster
- 29. MySQL Cluster ● “Shared-nothing”-Architecture ● Automatic partitioning ● Distributed fragments ● Synchronous replication ● Fast, automatic fail-over of data nodes ● Automatic resynchronisation ● Transparent to MySQL applicationen ● Supports transactions ● http://mysql.com/products/database/cluster/
- 30. MySQL Cluster ● In-memory indexes ● Not suitable for all query patterns (cross-table JOINs, range scans) ● No support for foreign keys ● Not suitable for long running transactions ● Network latency crucial ● Can be combined with MySQL replication (RBR)
- 32. MySQL Cluster & Replikation ● MySQL Cluster ● Easy failover from one MySQL node to another ● Scaling write load using multiple SQL nodes ● Asynchronous replication from Cluster to regular MySQL slaves ● Slaves take read load (InnoDB/MyISAM) ● Quick setup of new slaves (Cluster Online Backup) ● Easy failover and fast recovery
- 34. Galera Replication ● Patch for InnoDB plus external library ● Synchronous replication ● Single- or multi-master ● Multicast-Replication ● HA plus load sharing possible ● Certifikate-based replikation (instead of 2PC) ● http://codership.com/products/mysql_galera
- 35. MMM ● MySQL Master-Master Replication Manager ● Perl-Script for monitoring, failover and management ● Master-master replication configuration (one active writable master) ● Failover by moving virtual IP-Address ● Also supports read balancing ● http://mysql-mmm.org/
- 36. Continuent Tungsten Replicator ● Database-external solution ● Asynchronous, Master-Slave, Fan-out & Fan-in ● Java ● Log-based ● Events are stored in the Transaction History Log (THL) ● Modular architekture (Pipelines, Stages) ● http://continuent.com/community/tungsten-replicator
- 37. Red Hat Cluster Suite ● HA and load balancing ● Supports up to 16 nodes ● Shared storage ● Monitors services, file systems and network status ● Fencing (STONITH) or distributed lock manager ● Configuration synchronization ● http://www.redhat.com/cluster_suite/
- 38. Solaris Cluster / OpenHA Cluster ● Provides failover and scalability services ● Solaris / OpenSolaris (Project Colorado) ● Kernel-level components plus userland ● Agents monitor applications ● Geo Edition to provide Disaster Recovery using Replication ● Open Source since June 2007 ● http://hub.opensolaris.org/bin/view/Community+Group+ha-clusters/WebHome ● http://hub.opensolaris.org/bin/view/Project+ha-mysql/WebHome
- 39. Flipper ● Perl Script managing pairs of MySQL servers replicating to each other. ● Automatic switchover, triggered manually ● Enables one half of the pair to be taken offline for maintenance work while other half carries on ● Moves IP addresses based on a role ("read- only", "writable") ● http://provenscaling.com/software/flipper/
- 41. Thank you! Lenz Grimmer <lenz@grimmer.com> Twitter: @lenzgr http://lenzg.net/