I'm new to ATS, so far we've been using Squid, but due to it's instability are moving away.

I'm interested in avoiding regional cache duplication in CDN system. Currently, we have several Squid servers working as siblings and only pulling from origin if none of them has the object in cache, if sibling has object in cache, it's pulled from sibling but not stored locally. Only new content fetched from origin is store locally. Sibling lookup is done via ICP and has been working quite well so far.

Is similar setup possible with ATS?
I found no information in documentation how to configure siblings (only parent configuration is documented). Could you point me to right direction?