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: http://www.ecyrd.com/cassandracalculator/ On Thu, Oct 10, 2013 at 6:40 AM, Artur Kronenberg < artur.kronenb...@openmarket.com> 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 ken.hanc...@schange.com | www.schange.com | NASDAQ:SEAC<http://www.schange.com/en-US/Company/InvestorRelations.aspx> Office: +1 (978) 889-3329 | [image: Google Talk:] ken.hanc...@schange.com | [image: Skype:]hancockks | [image: Yahoo IM:]hancockks [image: LinkedIn]<http://www.linkedin.com/in/kenhancock> [image: SeaChange International] <http://www.schange.com/>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.
