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From Benjamin Black...@b3k.us>
Subject Re: Use of multiple Keyspaces
Date Thu, 08 Jul 2010 18:24:37 GMT
There is a memtable per CF, regardless of how many keyspaces you have.
 I'd pay more
attention to the delete/compaction side of things if you are going to
be doing that many
deletions.

Also, your mail client's formatting is broken.


b

On Thu, Jul 8, 2010 at 8:45 AM, Dwight Smith
<Dwight.Smith@alcatel-lucent.com> wrote:
> Hi
>
>
>
> 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 benefit.
>
>
>
> Comments please
>
>
>
> Thanks much
>
>
>
> Dwight
>
>
>
>
>
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