I'm curious if there are any efforts ongoing to amortize the background tasks in Cassandra over time? Specifically, the cost of compaction and AE, rebalancing, etc seems to be a problem for some users when they are expecting more steady-state performance. While this may sometimes be the result of a cluster which is at its marginal capacity, users are still surprised with the performance hit or downtime required for common operations. Making the cluster able to make finer-grained and measurable progress towards the ideal state may help other users, too.
Is there a feasible design or enhancement which may allow these types of background tasks to be broken apart into smaller pieces without compromising overall consistency? It would be excellent if the user could see the over-all state of the storage cluster, and to choose the proportion of resources allocated to recovering backlog vs servicing clients, etc. Even better, if there were some basic heuristics which worked well for the general case, and users would only have to see the scheduling plan in special situations. How would you go about doing that? Does the current architecture lend itself to this type of optimization, or otherwise?
