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From Kurtis vel <kurtisvela...@gmail.com>
Subject Re: Cassandra Data Loss
Date Fri, 10 Apr 2015 01:39:10 GMT
Hi Anuj,

Assuming cl=1 and rf=3.

Will the data ever be consistent if an asynchronous replication call fails?

Is this where read repair comes in handy?

thanks

On Thu, Apr 9, 2015 at 6:24 PM, Anuj Wadehra <anujw_2003@yahoo.co.in> wrote:

> Cl=1 means that client will only block for one response. In case of writes
> other 2 replicas will be updated asynchronously and eventually updated. As
> you are running heavy load make sure that writes /mutations are not getting
> dropped using nodetool tpstats on all nodes. Under heavy loads Cassandra
> may drop writes and as these were asynchronous,client wont know about that.
>
> if cl=1 for both reads and writes. Some reads may return stale data.If you
> need absolute guarantee that reads always return up to date data go for
> strong consistency r cf + w cf greater than rf. Eg read at quorum and write
> at quorum.
>
> Thanks
> Anuj Wadehra
>
> Sent from Yahoo Mail on Android
> <https://overview.mail.yahoo.com/mobile/?.src=Android>
> ------------------------------
>   *From*:"Pranay Agarwal" <agarwalpranaya@gmail.com>
> *Date*:Fri, 10 Apr, 2015 at 6:40 am
> *Subject*:Cassandra Data Loss
>
> Hi All.
>
>
> I am using 20 nodes cassandra cluster with RF=3 and CL=1. We are doing
> very write/read heavy operations (total 100k ops/sec).
>
> I have been assuming all along that all the data will be replicated in 3
> different place *irrespective of consistency level *as it's a very
> application/driver level config. Is that correct or Cassandra guarantees 3
> replica only when I also have CL as 3 as well?
>
>
> Thanks
> -Pranay
>

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