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October 9th, 2015 12:00
Best HA option - multiple clusters or multiple Protection Domains
When trying to design a system for the best high availability configuration, what is better:
* Multiple, independent ScaleIO clusters
--or--
* A single cluster with multiple Protection Domains?
I am concerned a single cluster might run into some unexpected issues and result in complete data loss for all SDS/SDCs. I don't know of what kind of event would cause this to happen, but I want to be on the safe side to ensure maximum HA. The only thing I can think of is when we loose the primary, secondary, and tie-breaker MDMs all at the same time. What other edge conditions are possible that would result in complete data loss for a cluster?
My gut tells me to run multiple ScaleIO clusters...
osaddict
110 Posts
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October 12th, 2015 10:00
The difference between running protection domains vs separate clusters is the metadata (MDM) cluster.
With protection domains, they are part of the MDM cluster running that cluster. In the current version, 3 nodes run that MDM cluster and if you have 2 of those nodes go down at the same time, you will have data unavailability. If you they are really un-recoverable, you could have data loss. The next release will enable the use of 5 nodes for MDMs.
With separate clusters, an MDM cluster is setup per cluster, as well as separate IM and gateway services. If the above scenario occurs, only one cluster would be affected. However, management operations would need to be done on each cluster separately, clients using storage from both cluster would need the client to be joined to both cluster and upgrades would have to be done on each cluster separately. As you can see, this adds a lot of complexity.