Design draft: fixing deletes and server side copy

[jammerdan]

@BrightSilence

My main concern with this would be that this concentrates all deletes in massive IO spikes on the storage node end. The lazy file walker will help in some occasions, but it doesn’t actually work on all IO schedulers.

Massive reads on startup

Even with storage2.piece-scan-on-startup: false we are seeing crazy massive reads on node startup. What is this?

Yeah it would be nice to get rid of all potential IO spikes.