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Sloppy Quorum - what is transferred to Node 4?

in this bit:

“… Thus, Dynamo transfers the replica stored on the failing node ( i.e., Server 1 ) to the next node of the consistent hash ring that does not have the replica ( i.e., Server 4 )…”

I am wondering if Node1 has failed, how can the system access its data to transfer to Node 4? or is it that Node 4 just starts a new file/db “delta”?

@Design_Gurus

Hi @milo_t

When a node fails, Dynamo transfer checks the next node that doesn’t have a replica of the failed node through consistent hashing. In our case, Server4 is not the replica of Server1 thus data is transferred to it.
Moreover, Server4 only stores the data temporarily along with the hint of the actual node(in the metadata) to whom the data belongs.

Thanks @Shaheryaar_Kamal, that’s exactly my point. If a node has failed, there is no way to access it! hence its data cant be copied to another server. (just imagine the server has caught fire, how would you access it??)I think what happens is that Dynamo starts a temporary file on Server 4, and it is merged into Server 1, when Server 1 comes back online.

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Yes @milo_t, you are correct :slight_smile:

I was going to ask the same question. I hope the authors will update the confusing text.


Course: Grokking the Advanced System Design Interview - Learn Interactively
Lesson: Replication - Grokking the Advanced System Design Interview