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From "Dwight Smith" <>
Subject Use of multiple Keyspaces
Date Thu, 08 Jul 2010 15:45:15 GMT


I am new to Cassandra and am preparing a data model for use in a
production environment, and need to decide if using multiple keyspaces
has any benefit.  


There are basically two types of data; the first,  large numbers (
~1750K) of entries which are written, very few reads, and then removed
after several seconds to several days. The keys are MD5 generated from
the content being written.  The second type, ~ 60K, entries written,
accessed with get_range_slices, then based on the time indicated in the
content, perform an action, then delete the specific entry from
Cassandra.  There are three columns for the second type, time to action
Key ( MD5 of action information ) - column TimeToScheduleAction, action
key to time - column ScheduledActionToTime, and finally action key to
action information - ActionToScheduledAction.


Currently these are members of two separate keyspaces.  Separate
keyspaces were chosen since the data volume was significantly different,
and as I understand, the memtables are dependent upon the data volume,
if KeysCached is not zero. Separate keyspaces would speed up the
memtable access for both.  In addition, it seems the compaction would
Comments please
Thanks much


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