The common practice is to size the Galera Cache based on write
volume measured during peak load, but often it is more of a
guesswork. The writeset cache capacity planning is crucial to
shorten the maintenance time and avoid long state transfers while
the cluster runs with reduced compute power. Now, if you could
understand what’s exactly inside the cache, wouldn’t the planning
be more aware as compared to only calculating the best size based
on wsrep_received/replicated_bytes variables?
Similarly, while dealing with various incidents occurring in Percona XtraDB Cluster or MariaDB Galera Cluster environments, how many times did you stumble upon the fact that the GCache file (galera.cache) is a black box and you can’t inspect it in a meaningful way?
In some scenarios, having the opportunity to see what exactly ended up in the cache file(s) could help us understand the write workload impact or what happened …
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