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https://issues.apache.org/jira/browse/CASSANDRA-2540?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Ellis resolved CASSANDRA-2540.
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Resolution: Won't Fix
Resolving in favor of that approach, which Vijay opened CASSANDRA-4705 for
> Data reads by default
> ---------------------
>
> Key: CASSANDRA-2540
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2540
> Project: Cassandra
> Issue Type: Wish
> Reporter: Stu Hood
> Assignee: Peter Schuller
> Priority: Minor
>
> The intention of digest vs data reads is to save bandwidth in the read path
> at the cost of latency, but I expect that this has been a premature
> optimization.
> * Data requested by a read will often be within an order of magnitude of the
> digest size, and a failed digest means extra roundtrips, more bandwidth
> * The [digest reads but not your data
> read|https://issues.apache.org/jira/browse/CASSANDRA-2282?focusedCommentId=13004656&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13004656]
> problem means failing QUORUM reads because a single node is unavailable, and
> would require eagerly re-requesting at some fraction of your timeout
> * Saving bandwidth in cross datacenter usecases comes at huge cost to
> latency, but since both constraints change proportionally (enough), the
> tradeoff is not clear
> Some options:
> # Add an option to use digest reads
> # Remove digest reads entirely (and/or punt and make them a runtime
> optimization based on data size in the future)
> # Continue to use digest reads, but send them to {{N - R}} nodes for
> (somewhat) more predicatable behavior with QUORUM
> \\
> The outcome of data-reads-by-default should be significantly improved
> latency, with a moderate increase in bandwidth usage for large reads.
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