our system need to use reliable collection as cache but dont want to have much memory pressure. Is reliable collection now supporting offloading data to local disk now? Cannot see find statement in official doc.
I used to read this Reliable Collection Caching as Cache in Service Fabric a
In short, yes. Quoting from the official documentation here (towards the middle of the page):
Persisted or Volatile: Data can be persisted to disk for durability against large-scale outages (for example, a datacenter power outage). Some Reliable Collections also support a volatile mode (with Caveats) where all data is kept in-memory, such as a replicated in-memory cache.
Further, at the bottom of this page, you can find more details about exactly which types of Reliable Collections can be persisted and/or be made volatile.