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From sal <>
Subject Re: Loading data on-demand in Cassandra
Date Thu, 08 Nov 2012 23:39:08 GMT
Pierre Chalamet <pierre <at>> writes:

> Hi,You do not need to have 700 Go of data in RAM. Cassandra is able to store
on disks and query from there if data is not cached in memory. Caches are
maintained by C* by itself but you still have to some configuration.Supposing
you want to store around 800 Go and with a RF=3, you will need at least 6
servers if you want to store all data of your db (keeping max 400 Go per server)
: 800x3/400=6.There is no native implementation of trigger in C*. Anyway, there
is an extension bringing this feature: This should allow you to be
notified of mutations (ie: not query). Some peoples on this ML are involved in
this, maybe they could help on this.Cheers,- Pierre
> From:  Oliver Plohmann <oliver <at>>
> Date: Sun, 12 Aug 2012 21:24:43 +0200
> To: <user <at>>
> ReplyTo:  user <at>
> Subject: Loading data on-demand in Cassandra
>     Hello,
>     I'm looking a bit into Cassandra to
>       see whether it would be something to go with for my company. I
>       searched through the Internet, looked through the FAQs, etc. but
>       there are still some few open questions. Hope I don't bother
>       anybody with the usual beginner questions ...
>     Is there a way to do load-on-demand
>       of data in Cassandra? For the time being, we cannot afford to
>       built up a cluster that holds our 700 GB SQL-Database in RAM. So
>       we need to be able to load data on-demand from our relational
>       database. Can this be done in Cassandra? Then there also needs to
>       be a way to unload data in order to reclaim RAM space. Would be
>       nice if it were possible to register for an asynchronous
>       notification in case some value was changed. Can this be done?
>     Thanks for any answers.
>       Regards, Oliver

I would consider looking into distributed caching technology (ehcache, gemfire)

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