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From Eldad Yamin <>
Subject Re: cassandra consistency level
Date Wed, 03 Aug 2011 06:59:34 GMT
So what you're saying is that no matter what consistency level I'm using,
the data will be written to all CF nodes right away, the consistency level
is just for making sure that all CF nodes are UP and all data is written.
In other words, if one of the nodes is down - the write (or read) will fail.

I'm asking that because I'm a bit worried with consistency, for example:
Every action that my client is doing is stored in a CF.x in a specific
column by his user_id.
I'm doing that by de-serializing the data that already found in the column,
adding new data (the action), serializing and storing the data.
so I'm worrying that some of the user actions will "drop" due
low-consistency when there are lots of changes to a specific column in a
sort period of time.
I know that I can solve this situation in a different way by storing each
action in a new column etc... but this is just an example that explain my
question in a simple way.


On Wed, Aug 3, 2011 at 3:21 AM, aaron morton <>wrote:

> Not sure I understand your question exactly, but will take a shot…
> Writes are sent to every UP node, the consistency level is how many nodes
> we require to complete before we say the request completed successfully. So
> we also make sure that CL nodes are UP before we start the request. If you
> run CL ALL then Replication Factor nodes must be up for each key you are
> writing.
> With the exception of CL ONE reads are also sent to all UP replicas.
> Hope that helps.
> -----------------
> Aaron Morton
> Freelance Cassandra Developer
> @aaronmorton
> On 3 Aug 2011, at 09:32, Eldad Yamin wrote:
> > Is consistency level "All" for write actually grenty that my data is
> updated in all of my node?
> > is it apply to read actions as-well?
> >
> > I've read it on the wiki, I just want to make sure.
> > Thanks!

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