Hi, > So how does this bit work? If one master falls over and slaves > move to master two, how do you rebuild master one without downtime? > Don't the slaves try and use Master 1 as soon as it's back > online even though its data is out of sync?
If master 1 fails and the slaves move to master 2, then they effectively swap roles as primary and secondary masters and the directive is issued to the webservers to connect in the reverse order. Yes, master 1 will be offline until it is rebuilt and will join again in the secondary role. The master connect wrapper is robust. If a connection fails it will try to reconnect a few times and run that query again. All the slaves and masters are on the same switch so if one fails, generally speaking, they all fail. > What if one of the slaves loses its heartbeat with master one and > falls over to master two when other slaves can still see master one. > Don't you then have inconsistencies in your data? The heartbeat code is pretty robust too. It's similar to the above wrapper and has the same benefits. Having said all that, I did mention that this is an inexpensive medium sized solution to availability and that it is a read-heavy, write-light DB scenario. Additionally there is no data of a financial nature (if there was, we would be using another set-up - commit / rollback for example..). As such we are tolerant to very small amounts of data loss in the event of a failover situation. On this, I refer you to the "how many 9's do you need" dscussion, nicely explained by Jeremy here: http://jeremy.zawodny.com/blog/archives/000805.html Cheers, Andrew -----Original Message----- From: Russell Horn [mailto:[EMAIL PROTECTED] Sent: Monday 02 February 2004 16:21 To: [EMAIL PROTECTED] Subject: RE: Advise on High Availability configuration Andrew Braithwaite wrote: > Each slave keeps a heartbeat to the master and in the event of a > failure, changes it's master to master2. So how does this bit work? If one master falls over and slaves move to master two, how do you rebuild master one without downtime? Don't the slaves try and use Master 1 as soon as it's back online even though its data is out of sync? What if one of the slaves loses its heartbeat with master one and falls over to master two when other slaves can still see master one. Don't you then have inconsistencies in your data? Russell. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
