[sheepdog] obbject placement

Corin Langosch info at corinlangosch.com
Sun Feb 8 20:46:01 CET 2015

Hi guys,

afaik sheepdog uses consistent hashing to map objects to nodes. But how do you choose where the individual ec-chunks of
an object should go? Consistent hashing cannot be used here because different ec-chunks of the same object might get
mapped to the same node.

I looked at the sources and got an idea: you calculate a "base" node for the object and then for each ec-chunk you add
its index. Example: we have 10 nodes (0..9), consistent hashing calculates node 7 for our object. As we have 4:2
encoding, we get the ec-chunks stored on [7,8,9,0,1,2]?

Is my assumption correct, or how do you actually do it?

Thanks for any help,

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