Is your feature request related to a problem? Please describe.

once objects with RS data and parity shards are produced (#3419), they should be placed into the container with enabled EC. Elements need to be distributed across SN as much as possible, ideally one SN per shard

Describe the solution you'd like

0. have container with REP 1 storage policy. Select n SNs from netmap for it as usual. Have K+R coded objects
1. sort SNs by first OID
2. store each i-th object in i mod N SN

Describe alternatives you've considered

not yet