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From TuxRacer69 <>
Subject newbie questions about Cassandra J. Ellis presentation
Date Fri, 13 Nov 2009 08:20:12 GMT
Hello Cassandra Users!

On the wiki page:
there is a link to J. Ellis pdf:

At page 41 we have: (Roadmap) Cassandra 0.5
Cassandra 0.5
Millions of columns per row
This will require another data format change

Question 1:
Is there any Jira logged for this change yet?
I'd like to understand
a) if a full data rebuild will be necessary for upgrading from 0.4.X to 0.5
b) what the limitations currently are in Cassandra.
- How many keys per column family
- How many columns per key in a standard column family
- How many columns per key in a super column family, and how many 
subcolumns within a supercolumn key

says "The main limitation on column and supercolumn size is that all 
data for a single key and column must fit (on disk) on a single machine 
in the cluster." but that does not really answer the questions above (as 
know we can have 1Tb disk cheaply)

Question 2:
Page 15 and 16: Architecture layer.
How could we defined Memtables and SStables? What the two 'S' stand for 
in SSTable?

Thanks a lot

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