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 > >
