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From "Stu Hood (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (CASSANDRA-2455) Improve counter disk usage
Date Wed, 20 Apr 2011 08:09:05 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-2455?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Stu Hood resolved CASSANDRA-2455.
---------------------------------

    Resolution: Incomplete

I can't see any non-invasive solutions to this problem, so I'm focusing on CASSANDRA-674.

> Improve counter disk usage
> --------------------------
>
>                 Key: CASSANDRA-2455
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2455
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Stu Hood
>
> Counter values currently use a huge amount of space on disk:
> {code}
> (header + length + RF * (nodeid + count + clock))
> ==
> (2 + 2 + RF * (16 + 8 + 8)) bytes
> {code}
> Type specific compression (as on CASSANDRA-2398) is a long term solution to this problem,
but we need a short term fix to make a large volume of counters possible.
> The largest and most redundant part of the counter is the nodeid, which is now 16 bytes
per replica. One proposed improvement would be keep a per-sstable dictionary of all replica
sets, and to assume the replicas are sorted by nodeid in the counter value. This would allow
us to encode the replica set as a single integer in the counter value, and to use it to look
up the actual replicas in the dictionary. Assuming an integer replica set id, you could allow
for 2^32 replica changes with 4 total bytes of overhead in each counter:
> {code}
> (header + length + replicasetid + RF (count + clock))
> ==
> (2 + 2 + 4 + RF * (8 + 8)) bytes
> {code}

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