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Re: Multi-master & Multi data-paths
Posted by: Rick James
Date: May 31, 2010 10:34AM

HA, as in minimal downtime?
HA, as in minimal latency?

Many things could go wrong; your designs cover only a few of the possibilities.

* Power outage -- UPS (but that has limits)
* Heavy 'read' load -- Slave(s)
* Heavy 'write' load -- Sharding (not dual-master, which does not help in heavy write load)
* Disk drive failure -- RAID mirroring or parity
* Controller/RAM/motherboard failure -- multiple servers
* CPU failure -- multiple cpus
* High disk writes -- RAID with battery-backed-write-cache
* Network failure -- ?
* Software corruption of the data -- backups
* Flood/earthquake/etc destroys data center -- have servers geographically separated.

My preference --
* Dual-master, but write to only one.
* Fail-over plan for switching to the other master -- requires clients to re-point, requires removing dead (or isolated) master from network during repairs, etc.
* If partial network outage, do not assume the master is dead; it could be alive and receiving writes... If you allow the other master to take writes, that could lead to nasty inconsistencies between the masters.

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Re: Multi-master & Multi data-paths
May 31, 2010 10:34AM


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