1.) 16 to 24GB out of how much total system memory? Is this 50% of available system RAM or 90%?
Thanks for the reply! -Aaron On Mon, Aug 2, 2010 at 2:24 PM, Aaron Morton <aa...@thelastpickle.com>wrote: > Will answer as best I can, others will know more. > > 1) Most people seem to lean towards more memory for the JVM, around 16 to > 24gb. Memory is also used by the MemTables and I assume during the > compaction processes. > > 2) Cannot say for sure, but I assume so. Think I've seen the cache with > data in it when I have only done writes. > > 3) I've noticed large differences between nodes when using the RP and > automatic token assignments, such as the last node with very little data. > Try setting tokens at start up, see > http://wiki.apache.org/cassandra/Operations > > 3.5) Yes load balance restores things, I suggest you run it on one node at > a time. Start with the node with the lowest load. Watching the progress by > watching the streams via JMX or nodetool. > > Hope that helps. > Aaron > > > > On 03 Aug, 2010,at 07:28 AM, Aaron Blew <aaronb...@gmail.com> wrote: > > Hi All, > I've got a couple questions that have come up about how Cassandra works and > what others are seeing in their environments. Here goes: > > 1.) What have you found to be the best ratio of Cassandra row cache to > memory free on the system for filesystem cache? Are you tuning it like an > RDBMS so Cassandra has the vast majority of the RAM in the system or are you > letting the filesystem cache do some of the work? > > 2.) Is the Cassandra cache write-through (ie are new records held in the > row cache as they're written to disk? > > 3.) When using the random partitioner how much difference should be > expected (or has been observed) between nodes? 2%? 10%? > > 3.5) Can a load balance be expected to bring the data distribution pretty > close to even among all nodes in the ring? Is the correct process for a > loadbalance to run the loadbalance operation on each node in the ring? > > > Thanks! I'm curious to hear what other's have observed. > -Aaron > >
