Comment by saurik

Is it really a problem to bubble up that error (and kill the database server) if you can just bring up a new database server with a clean cache (potentially even on the same computer without rebooting it) instantly? (I have been doing this kind of thing using bcache over a raid array of EBS drives on Amazon for around a decade now, and I was surprised you were so concerned about those read failures so heavily to forgo the LRU benefits when to me your solution sounds absolutely brutal for needing a complete copy of the remote disk on the local "cache" disk at all times for the RAID array to operate at all, meaning it will be much harder to quickly recover from other hardware failures.)