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From aaron morton <aa...@thelastpickle.com>
Subject Re: Cassandra as in-memory cache
Date Sun, 11 Sep 2011 21:32:27 GMT
If the row cache is enabled the read path will not use the sstables. Depending on the workload
I would then look at setting *low* memtable flush settings to use as much memory as possible
for the row cache. If the row is in the row cache the read path will not look at SSTables.


Then set the row cache save settings per CF to ensure the cache is warmed when the node starts.


The write path will still use the WAL so if you may want to disable the commit log using the
durable_writes setting on  the keyspace. 

Hope that helps. 

-----------------
Aaron Morton
Freelance Cassandra Developer
@aaronmorton
http://www.thelastpickle.com

On 10/09/2011, at 4:38 AM, kapil nayar wrote:

> Hi,
> 
> Can we configure some column-families (or keyspaces) in Cassandra to perform as a pure
in-memory cache? 
> 
> The feature should let the memtables always be in-memory (never flushed to the disk -
sstables).
> The memtable flush threshold settings of time/ memory/ operations can be set to a max
value to achieve this. 
> 
> However, it seems uneven distribution of the keys across the nodes in the cluster could
lead to java error no-memory available. In order to prevent this error can we overflow some
entries to the disk?
> 
> Thanks,
> Kapil


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