On Fri, Feb 5, 2010 at 4:51 PM, Brian Frank Cooper <coop...@yahoo-inc.com> wrote: > Yes, I had used the default 0.1. > > These boxes have 8 GB of RAM and I was giving 6 GB to the JVM (-Xmx). Does > Cassandra do a read caching of data? It seems from the text in storage.conf > that keys cache fraction refers only to indexing the keys, not caching the > content. So I would imagine increasing the keys cached fraction would > decrease the memory used for data caching
0.5 doesn't do data caching (except what you get for free from the OS). 0.6 will change this, but for 0.5 things are nice and simple. :) So a large heap can actually make things worse if it makes the GC lazy and the OS can't use that to cache data. If your data set is larger than 5GB on disk I would say give it KeysCachedFraction of 0.2, 3GB JVM heap. Otherwise 0.4 and 5GB. -Jonathan
