incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Ken Hancock <>
Subject Re: Rowcache and quorum reads cassandra
Date Thu, 10 Oct 2013 13:06:01 GMT
If you're hitting 3/5 nodes, it sounds like you've set your replication
factor to 5. Is that what you're doing so you can have a 2-node outtage?

For a 5-node cluster, RF=5, each node will have 100% of your data (a second
DC is just a clone), so with a 3GB off-heap it means that 3GB / <total data
size in GB> total would be cacheable in the row cache.

On the other hand, if you're doing RF=3, each node will have 60% of your
data instead of 100% so the effective percentage of rows that are cache
goes up by 66%.

Great quick & dirty caclulator:

On Thu, Oct 10, 2013 at 6:40 AM, Artur Kronenberg <> wrote:

>  I was reading through configuration tips for cassandra and decided to
> use row-cache in order to optimize the read performance on my cluster.
> I have a cluster of 10 nodes, each of them opeartion with 3 GB off-heap
> using cassandra 2.4.1. I am doing local quorum reads, which means that I
> will hit 3 nodes out of 5 because I split my 10 nodes into two data-centres.
> I was under the impression that since each node gets a certain range of
> reads my total amount of off-heap would be 10 * 3 GB = 30 GB. However is
> this still correct with quorum reads? How does cassandra handle row-cache
> hits in combination with quorum reads?
> Thanks!
> -- artur

*Ken Hancock *| System Architect, Advanced Advertising
SeaChange International
50 Nagog Park
Acton, Massachusetts 01720 | |

Office: +1 (978) 889-3329 | [image: Google Talk:] | [image:
Skype:]hancockks | [image: Yahoo IM:]hancockks [image:

[image: SeaChange International]
 <>This e-mail and any attachments may contain
information which is SeaChange International confidential. The information
enclosed is intended only for the addressees herein and may not be copied
or forwarded without permission from SeaChange International.

View raw message