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From "Chris Goffinet (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-2045) Simplify HH to decrease read load when nodes come back
Date Mon, 24 Jan 2011 23:05:47 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2045?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12986087#action_12986087
] 

Chris Goffinet commented on CASSANDRA-2045:
-------------------------------------------

No, storing a pointer is not almost free. The trade off you make is read performance when
nodes come back up. At the moment read performance could very well cause cascading failures
too. You trade storage vs I/O.  Nodes down for long periods of time, would have a bigger impact
on the nodes trying to send HH data.

Aren't we sending the entire row as well? We might be doing paging but if I modify 1 column,
and it has 1M columns, 1M + 1 columns still get sent? I would agree to having it be tunable,
but I prefer performance consistency over storage when it comes to I/O.

> Simplify HH to decrease read load when nodes come back
> ------------------------------------------------------
>
>                 Key: CASSANDRA-2045
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2045
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Chris Goffinet
>             Fix For: 0.7.2
>
>
> Currently when HH is enabled, hints are stored, and when a node comes back, we begin
sending that node data. We do a lookup on the local node for the row to send. To help reduce
read load (if a node is offline for long period of time) we should store the data we want
forward the node locally instead. We wouldn't have to do any lookups, just take byte[] and
send to the destination.

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