Thank you very much Andras. I will try MX4J tomorrow. Also thanks for the pointers on nodetool. I just poked around a bit, and found that "info" would give you the cache statistics, and there are also "invalidatekeycache" and "invalidaterowcache". I think these are exactly what I need.
-- Y. On Tue, Nov 27, 2012 at 12:14 AM, Andras Szerdahelyi < andras.szerdahe...@ignitionone.com> wrote: > If its the RMI horror ( registry port + actual port ) you are worried > about, enabling MX4J in cassandra-env.sh for the HTTP transport ( > http://wiki.apache.org/cassandra/Operations#Monitoring_with_MX4J ) could > help although i never used it myself. Or you can just throw in the Jolokia > JVM agent http://www.jolokia.org which will do roughly the same > > i'm not aware of the hit rate or any of the other cf/system metrics > being exposed over anything other than JMX, sorry. You can poke around with > nodetool on the nodes themselves ( that uses JMX itself ) to get other > metrics, but i have not been able to get cache stats out of nodetool > cfstats. I think it might be because they are no longer on the CF's mbean. > > regards, > Andras > > On 27 Nov 2012, at 05:22, Yiming Sun <yiming....@gmail.com> wrote: > > Interesting -- I completely overlooked the OS cache aspect, but how long > does the OS keep cached pages? It seems they reside in memory for 4 hours > at least (which happens to be the default time for key cache).. The CF has > over 2.6 million rows, and I am only fetching a random set of 5000 each > time. > > Where else can I examine the cache hit ratio? The nodes are remote > servers behind some strict university controlled firewall, so it wouldn't > be easy for me to tap in using JConsole. Thanks. > > -- Y. > > > On Mon, Nov 26, 2012 at 11:06 PM, Andras Szerdahelyi < > andras.szerdahe...@ignitionone.com> wrote: > >> >> SSTables in http://en.wikipedia.org/wiki/Page_cache maybe? >> How many rows do you have in this CF? Are you getting all columns? >> >> What do the cassandra.db mbeans say ( hit ratio, cache requests, items >> etc ) >> >> regards, >> Andras >> >> On 27 Nov 2012, at 04:12, Yiming Sun <yiming....@gmail.com> wrote: >> >> > Hi, >> > >> > I am carrying out some performance test against a 6-node cassandra >> cluster (v1.1.0), and need to disable the key cache entirely as one of the >> scenarios. >> > >> > However, by setting key_cache_size_in_mb to 0, I am still seeing >> caching effects. For example, when I fetch a set of 5000 rows, the first >> time it would deliver at about 60MB/sec, but all subsequent fetches (even >> after fetching several other sets), it would deliver at about 120MB/sec. >> This is exactly the same behavior I have observed when the >> key_cache_size_in_mb was left blank. >> > >> > So I am just wondering how I can disable the key cache entirely. All >> our nodes have JNA.jar deployed -- not sure it this has anything to do with >> what I saw. Thanks. >> > >> > -- Y >> >> > >
