Thanks Aaron! Through the commands "top" and "iostats", I find the IO system is not overloaded yet. So I will check the data model.
And how to get the row size of a specific key? Do we have the api yet? Thanks. -- Dikang Gu 0086 - 18611140205 On Sunday, May 22, 2011 at 6:15 PM, aaron morton wrote: > It's hard to say the latency is to high without knowing how many columns and > how many bytes you are asking for. It's also handy to know what the query > looks like, i.e. is it a slice or a get by name, and the CF level > > Latency reported at the CF or KS level are for local read / write operations. > Do all nodes in the cluster show similar values or just this one? If you are > looking for it the o.a.c.db.StorageProxy MBean has the latency trackers for > the cluster wide requests. > > If you are looking for a quick speed bump consider enabling the row cache. It > looks like you have a small hot set, they key cache has only 611 entries and > gets a 90%+ hit rate and the average row is 144KB. You will need more memory > though. > > If you want to dig deeper into it: > - make sure the app making the correct query and not wasting effort > - watch TP stats to see if the server is keeping up with other things > - check if the IO system is overloaded (google is your friend) > > I'd start with the data model and the query. > > Hope that helps. > > ----------------- > ----------------- > Aaron Morton > Freelance Cassandra Developer > @aaronmorton > http://www.thelastpickle.com > > > > > > On 20 May 2011, at 20:32, Dikang Gu wrote: > > I use the default consistency level in the hector client, so it should be > > QUORUM. > > > > -- > > Dikang Gu > > 0086 - 18611140205 > > On Friday, May 20, 2011 at 4:25 PM, Jeffrey Kesselman wrote: > > > What consistency are you asking for? > > > > > > On Fri, May 20, 2011 at 7:42 AM, Dikang Gu <dikan...@gmail.com> wrote: > > > > Hi All, > > > > I'm running three cassandra 0.7.4 nodes in a cluster, and I give 2G > > > > memory > > > > to each node. > > > > Now, I get the cfstats here: > > > > Keyspace: UserMap > > > > Read Count: 38411 > > > > Read Latency: 123.54214613001484 ms. > > > > Write Count: 44155 > > > > Write Latency: 0.02341093873853471 ms. > > > > Pending Tasks: 0 > > > > Column Family: Map > > > > SSTable count: 3 > > > > Space used (live): 32704387 > > > > Space used (total): 32704387 > > > > Memtable Columns Count: 49 > > > > Memtable Data Size: 3348 > > > > Memtable Switch Count: 56 > > > > Read Count: 38411 > > > > Read Latency: 123.542 ms. > > > > Write Count: 44155 > > > > Write Latency: 0.023 ms. > > > > Pending Tasks: 0 > > > > Key cache capacity: 200000 > > > > Key cache size: 611 > > > > Key cache hit rate: 0.9294361241314483 > > > > Row cache: disabled > > > > Compacted row minimum size: 125 > > > > Compacted row maximum size: 17436917 > > > > Compacted row mean size: 147647 > > > > You can find that the Read Latency is really high here, so what can I > > > > do to > > > > reduce the latency? Give more memory to the three nodes? Any other > > > > options? > > > > Thanks. > > > > -- > > > > Dikang Gu > > > > 0086 - 18611140205 > > > > > > > > > > > > -- > > > It's always darkest just before you are eaten by a grue. > > > > > >
