With 8GB RAM, the default heap size is 2GB, so you will quickly start running out of heap space if you do large reads. What is a large read? It depends on the number of columns in each row and data in each column. It could 100,000 rows for some and 300,000 for others. In addition, remember that Java adds a lot of overhead to data in memory, so a 8 character string will not occupy just 8 bytes in memory, but a lot more.
In general, avoid large reads in C*. If it is absolutely must and you cannot repartition the data, then use a driver that supports paging. Mohammed From: Umang Shah [mailto:shahuma...@gmail.com] Sent: Wednesday, October 15, 2014 10:46 PM To: user@cassandra.apache.org Subject: What will be system configuration for retrieving few "GB" of data Hi, I am facing many problem after storing certain limit of records in cassandra, and giving outofmemoryerror. I have 8GB of RAM in my system, so how much records i can expect to retrieve by using select query? and what will be the configuration for those people who are retrieving 15-20 GB of data? Can somebody explain me how to improve read performance then it will be great help, i tried http://www.datastax.com/documentation/cassandra/2.0/cassandra/operations/ops_tune_jvm_c.html such things but no help. -- Regards, Umang Shah shahuma...@gmail.com<mailto:shahuma...@gmail.com>
