Comments on: High Availability vs. Fault Tolerance: Is FT’s 00.001% Edge in Uptime Worth the Headache? https://www.percona.com/blog/high-availability-vs-fault-tolerance/ Thu, 14 Dec 2023 22:33:22 +0000 hourly 1 https://wordpress.org/?v=6.5.2 By: Paul https://www.percona.com/blog/high-availability-vs-fault-tolerance/#comment-10974207 Tue, 14 Nov 2023 22:12:41 +0000 https://www.percona.com/blog/?p=90415#comment-10974207 In this article you summarize the differences between HA and FT but neglect to explain why a system designer would choose FT. The tradeoffs described don’t explain clearly to one unfamiliar with the nomenclature that an HA system can only operate in a degraded state during faults unless consistency can be safely repaired afterward. An HA system desiring consistency must reliably detect the cluster state and reject writes during any fault that might involve a network partition if it is to maintain consistency.

The biggest challenge in the FT vs HA tradeoff is determining where consistency is required and how strictly it must be maintained. Systems handling financial data usually can’t afford to be inconsistent, even temporarily, which is a large part of why they have been so slow to adopt distributed architectures, instead preferring DR where there is only one possible history of transactions.

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