This document provides an overview and summary of various high availability (HA) solutions for MySQL databases. It begins with an introduction to HA and definitions of key terms. It then discusses MySQL replication, including asynchronous, semi-synchronous, and features in MySQL 5.6 and MariaDB 10.0. Other HA solutions covered include MHA for automated failover, Galera/MariaDB Galera Cluster for synchronous replication, shared disk solutions like DRBD, and MySQL Cluster for in-memory synchronous replication across nodes. The document provides brief descriptions of how each solution works and when it may be applicable.

1. HA&Solu4ons&for&MySQL&
Joffrey&Michaie&
Consultant&
SkySQL&AB&©&2013&Confiden4al&

2. Agenda&
• Introduc4on&
• MySQL&Replica4on&
• SemiHSynchronous&Replica4on&
• MySQL&5.6&
• MariaDB&10.0&
• MHA&
• Galera&
• Shared&Disk&
• DRBD&
• MySQL&Cluster&
SkySQL&AB&©&2013&Confiden4al&

3. Introduc4on&to&HA&
“High&availability&is&a&system&design&protocol&and&
associated&implementa6on&that&ensures&a&certain&
degree&of&opera6onal&con6nuity&during&a&given&
measurement&period”&
SkySQL&AB&©&2013&Confiden4al&

4. Up4me,&Down4me,&9s&
Availability&=&up4me&/&(up4me&+&down4me)&
&
&90%& &
&
&
&
&1&nine&&
&
&
&36.5&days&/&year &&
&
&99%& &
&
&
&
&2&nines& &
&
&3.65&days&/&year&
&
&99.9%&&
&
&
&
&3&nines& &
&
&8.76&hours&/&year&
&
&99.99%& &
&
&
&4&nines& &
&
&52&minutes&/&year&
&
&99.999%& &
&
&
&5&nines& &
&
&5&minutes&/&year&
&
&99.9999%&&
&
&
&6&nines& &
&
&31&seconds&/&year&
Availability&=&MTBF&/&(MTBF&+&MTTR)&
SkySQL&AB&©&2013&Confiden4al&

5. Terminology&
• Synchronous&vs.&Asynchronous&
• SharedHDisk&vs.&SharedHNothing&vs.&SharedHMemory&
• Single&Point&Of&Failure&H&SPOF&
• Failover&vs.&Switchover&
• Split&Brain&
• Node&Fencing,&STONITH,&Quorum&
SkySQL&AB&©&2013&Confiden4al&

6. Designing&for&HA&
• Which&level&of&availability&do&I&need?&
• How&many&nines?&
• Do&I&require&no&loss&of&data?&
• Could&I&loose&some&transac4ons?&
• Will&my&users&no4ce&or&care?&
• Do&I&need&automa4c&failover&or&is&manual&switchover&ok?&
• How&do&I&test&this?&
• Can&I&provide&a&reasonable&service&when&X&is&down?&
• Replace&X&with&each&component&of&the&service&
SkySQL&AB&©&2013&Confiden4al&

7. Before&we&talk&about&solu4ons&
• A&high&availability&setup&does&not&
replace&backups&
• Check&parameters&
• flush_at_trx_commit&
• sync_binlog&
• expire_logs_day&
• binlog_format&
• sync_master_info&(on&slaves)&
• ...&
• Requirements&for&parameters&may&
change&if&using&baieryHbacked&disk&
cache&
SkySQL&AB&©&2013&Confiden4al&

8. MySQL&Replica4on&H&Asynchronous&
• Asynchronous:&3&Phases&
1. Commit&and&write&to&binlog&on&Master&
2. Ship&changes&to&relay&log&on&slave&
3. Apply&changes&on&slave&&
• Master&H>&slave&rela4onship&
• MonoHthreaded&on&slaves&un4l&MySQL&5.5&
• MySQL&5.6&allows&mul4Hthreaded&
• No&conflict&resolu4on&
• MasterHmaster&replica4on&or&circular&
replica4on&need&applica4on&logic&
&
SkySQL&AB&©&2013&Confiden4al&
Slave(s)&
Master&

9. MySQL&Replica4on&–&SemiHSynchronous&
• Added&as&a&plugin&in&MySQL®&5.5&
• Ensures&that&changes&have&been&shipped&to&
at&least&one&slave&(or&4meouts)&&
• A&COMMIT&on&the&master&waits&for&ONE&
Slave&to&acknowledge&the&transac4on&
• Important:&The&Master&does&not&wait&for&the&
Slave&to&execute&the&transac4on,&only&to&write&
it&to&the&relay&log&
• So&the&Slave&SQL&Thread&may&s4ll&lag&behind&
the&Master&and&queries&to&the&Slave&may&s4ll&
return&old&data&
• Poten4ally&adds&latency&to&queries&
SkySQL&AB&©&2013&Confiden4al&
Slave(s)&
Master&

10. MySQL&Replica4on&for&HA&
• Master&<H>&standby&master&H&manual&failover&
• Minimal&down4me&for&changes&and&upgrades&
• SemiHsynchronous&should&be&used&
• Used&in&combina4on&with&other&HA&solu4ons&
for&geographical&replica4on&
SkySQL&AB&©&2013&Confiden4al&

11. MySQL®&5.6&–&New&Replica4on&Features&
• Global&Transac4on&ID&(GTID)&
• Makes&it&easy&to&automate&failover&and&slave&promo4on&
• Replica4on&failover&and&admin&u4li4es&
• Mul4Hthreaded&slaves&
• Replica4on&event&checksums&
• TimeHdelayed&replica4on&
SkySQL&AB&©&2013&Confiden4al&

12. MariaDB&10.0&–&New&Replica4on&Features&
• Mul4Hsource&replica4on&
• Global&Transac4on&ID&(GTID)&
• Different&implementa4on&from&MySQL&5.6&
• GTID&per&domain&instead&of&server&
SkySQL&AB&©&2013&Confiden4al&

13. MHA&
Master&High&Availability&Manager&
• Automates&master&failover&and&slave&
promo4on&
• Monitors&the&master&or&can&integrate&with&
Pacemaker/Heartbeat&
• Failover&is&an&online&opera4on&
• Also&allows&manual&switchover&
• Short&down4me:&open&a&few&seconds&
• MySQLHReplica4on&consistency&
• No&performance&penalty&
• Drop&in&solu4on&on&exis4ng&deployment&
&
SkySQL&AB&©&2013&Confiden4al&

14. MHA&
Failover&Process&
1. Aiempt&to&contact&MySQL&master&server&
by&SSH&
2. If&master&server&is&alive&access&the&binary&
log&and&recover&events&
3. Find&the&slave&with&the&most&advanced&
relay&log&
4. Sync&all&slaves&to&the&latest&available&
binlog&event&
5. STONITH&master&if&necessary&
6. Promote&slave&to&master&
SkySQL&AB&©&2013&Confiden4al&

15. Galera&/&MariaDB&Galera&Cluster&
• Provides&“virtually”&synchronous&
Clients
replica4on&
• Works&with&InnoDB&
• No&slave&lag&
• Transac4ons&are&validated&by&slaves&
upon&commit&
• Cer4fica4on&and&quorum&
• Transac4ons&may&be&rolled&back&
at&this&stage&
• Mul4Hmaster&or&masterHslave&possible&
SkySQL&AB&©&2013&Confiden4al&
MySQL
MySQL
MySQL
wsrep
wsrep
wsrep
Galera Replication

16. Galera&/&MariaDB&Galera&Cluster&
• Provides&“virtually”&synchronous&
Clients
replica4on&
• Works&with&InnoDB&
• No&slave&lag&
• Transac4ons&are&validated&by&slaves&
upon&commit&
• Cer4fica4on&and&quorum&
• Transac4ons&may&be&rolled&back&
at&this&stage&
• Mul4Hmaster&or&masterHslave&possible&
SkySQL&AB&©&2013&Confiden4al&
MySQL
MySQL
MySQL
wsrep
wsrep
wsrep
Galera Replication

17. Galera&–&Transac4on&Process&
• Transac4on&is&processed&
locally&up&to&commit&4me&
Client
trx
MySQL
MySQL
MySQL
wsrep
wsrep
wsrep
Galera Replication
SkySQL&AB&©&2013&Confiden4al&

18. Galera&–&Transac4on&Process&
• Transac4on&is&processed&
locally&up&to&commit&4me&
Client
• Transac4on&is&replicated&
to&whole&cluster&
trx
MySQL
MySQL
MySQL
wsrep
wsrep
wsrep
ws
Galera Replication
SkySQL&AB&©&2013&Confiden4al&
ws

19. Galera&–&Transac4on&Process&
• Transac4on&is&processed&
locally&up&to&commit&4me&
Client
• Transac4on&is&replicated&
to&whole&cluster&
• Client&gets&OK&status&
trx
MySQL
MySQL
MySQL
wsrep
wsrep
wsrep
Galera Replication
SkySQL&AB&©&2013&Confiden4al&

20. Galera&–&Transac4on&Process&
• Transac4on&is&processed&
locally&up&to&commit&4me&
Client
• Transac4on&is&replicated&
to&whole&cluster&
• Client&gets&OK&status&
• Transac4on&is&applied&in&
slaves&
MySQL
MySQL
trx
wsrep
wsrep
Galera Replication
SkySQL&AB&©&2013&Confiden4al&
MySQL
trx
wsrep

21. SharedHdisk&Solu4on&
• Ac4ve&–&Passive&replica4on&
• Failover&requires&MySQL&crash&recovery&(and&
open&file&system&crash&recovery)&
• Combined&with&Pacemaker/Heartbeat&for&
automa4c&failover&
• Virtual&IP&most&open&used&to&fail&over&
• In&theory&the&SAN&is&a&SPOF&
SkySQL&AB&©&2013&Confiden4al&

22. DRBD®&&
• Synchronous&replica4on&(three&modes)&
• Ac4ve&–&Passive&replica4on&
• Failover&requires&MySQL&crash&recovery&(and&
open&file&system&crash&recovery)&
• Combined&with&Pacemaker/Heartbeat&for&
automa4c&failover&
• Virtual&IP&most&open&used&to&fail&over&
• STONITH&or&other&fencing&mechanism&
needed&to&avoid&splitHbrain&scenarios&
• Available&on&Linux&
SkySQL&AB&©&2013&Confiden4al&

23. DRBD®&H&Architecture&
SkySQL&AB&©&2013&Confiden4al&

24. MySQL&Cluster&H&Features&
• Synchronous&replica4on&between&
nodes&
• Through&TwoHPhase&Commit&Protocol&
• ACID&transac4ons&
• Row&level&locking&
• Shared&nothing&architecture&
• No&single&point&of&failure&
• Automa4c&failover&
SkySQL&AB&©&2013&Confiden4al&
• InHmemory&storage&
• Some&data&can&be&stored&on&disk&
• Checkpoin4ng&to&disk&for&durability&
• Two&types&of&indexes&
• Ordered&THtrees&
• Unique&hash&indexes&
• Online&opera4ons&
• Add&node&groups&
• Sopware&upgrade&
• Some&table&altera4ons&

25. MySQL&Cluster&H&Architecture&
SkySQL&AB&©&2013&Confiden4al&

26. MySQL&Cluster&H&Par44oning&
SkySQL&AB&©&2013&Confiden4al&

27. MySQL&Cluster&
Network&par44oning&protocol&
Designed&to&avoid&splitHbrain&
1. Is&at&least&one&node&from&each&node&group&present?&&
• If&not&then&the&cluster&cannot&con4nue&H&shutdown&
2. Are&all&nodes&present&from&any&node&group?&
• If&so&then&this&is&the&only&viable&cluster&H&con4nue&
3. Ask&the&arbitrator&
• The&arbitrator&decides&which&”cluster”&con4nues&
• If&the&arbitrator&is&not&available&the&cluster&will&shutdown&
SkySQL&AB&©&2013&Confiden4al&

28. Where&does&MySQL&Cluster&fit?&
• High&demands&on&availability&(5&nines)&
• You&need&write&scalability&
• You&have&3&or&more&”machines”&available&
• Where&the&queries&and&data&model&are&simple&
• When&the&data&fits&in&memory&
• When&you&have&skilled&people&
SkySQL&AB&©&2013&Confiden4al&

29. Geographical&Replica4on&
• For&geographical&(mul4Hsite)&redundacy&
synchronous&solu4ons&are&open&not&
desirable&
• Standard&Replica4on&can&be&combined&
with&any&synchronous&solu4on&locally&
• MySQL&Cluster&
• DRBD&/&shared&disk&
• Galera&
SkySQL&AB&©&2013&Confiden4al&

30. Geographical&Replica4on&
MySQL&Cluster&
• MySQL&Cluster&has&addi4onal&features&
related&to&Geographical&replica4on&
• Conflict&detec4on&and&automa4c&
resolu4on&
• Several&possible&resolu4on&methods&exist&
• Mul4ple&replica4on&channels&possible&
• Mul4Hsource&replica4on&possible&
• Binlog&injec4on&ensures&the&consitency&
of&binlogs&
SkySQL&AB&©&2013&Confiden4al&

31. Quick&Comparison&Chart&
*
SkySQL&AB&©&2013&Confiden4al&

32. Quick&Comparison&Chart&
SkySQL&AB&©&2013&Confiden4al&

33. Ques4ons?&
SkySQL&AB&©&2013&Confiden4al&

34. Thank&you!&
Joffrey&Michaie&
Joffrey.michaie@skysql.com&
SkySQL&Ab&
www.skysql.com&
www.facebook.com/skysql&
www.linkedin.com/company/skysql&
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Ab.
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SkySQL&AB&©&2013&Confiden4al&