> Running a query to like “select * from <table_name> where atag=<foo>”, where > ‘atag’ is the first column of the composite key, from either JDBC or Hector > (equivalent code), results in read times of 200-300ms from a remote host on > the same network.
If you send a query to select columns from a row and do not fully specify the row key cassandra has to do a row scan. If you want fast performance specify the full row key. > Using read consistency of ONE reduces the read latency by ~20ms, compared to > using QUORUM. It would only have read from the local node. (I think, may be confusing secondary index reads here). Cheers ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 3/10/2012, at 2:17 AM, Roshni Rajagopal <roshni_rajago...@hotmail.com> wrote: > Arindam, > > Did you also try the cassandra stress tool & compare results? > > I havent done a performance test as yet, the only ones published on the > internet are of YCSB on an older version of apache cassandra, and it doesn't > seem to be actively supported or updated > http://www.brianfrankcooper.net/pubs/ycsb-v4.pdf. > > The numbers you have sound very low, for a read of a row by key which should > have been the fastest. I hope someone can help investigate or share numbers > from their tests. > > > > Regards, > Roshni > > > > From: dean.hil...@nrel.gov > > To: user@cassandra.apache.org > > Date: Tue, 2 Oct 2012 06:41:09 -0600 > > Subject: Re: Read latency issue > > > > Interesting results. With PlayOrm, we did a 6 node test of reading 100 rows > > from 1,000,000 using PlayOrm Scalable SQL. It only took 60ms. Maybe we have > > better hardware though??? We are using 7200 RPM drives so nothing fancy on > > the disk side of things. More nodes puts at a higher throughput though as > > reading from more disks will be faster. Anyways, you may want to play with > > more nodes and re-run. If you run a test with PlayOrm, I would love to know > > the results there as well. > > > > Later, > > Dean > > > > From: Arindam Barua <aba...@247-inc.com<mailto:aba...@247-inc.com>> > > Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" > > <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> > > Date: Monday, October 1, 2012 4:57 PM > > To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" > > <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> > > Subject: Read latency issue > > > > unning a query to like “select * from <table_name> where atag=<foo>”, where > > ‘atag’ is the first column of the composite key, from either JDBC or Hector > > (equivalent code), results in read times of 200-300ms from a remote host on > > the same network. The query returned around 800 results. Running the same > > query on a Cassandra host results in a read time of ~110-130 ms. > > Using read consistency of ONE reduces the read latency by ~20ms, compared > > to using QUORUM. > > > > Enabling row cache did not seem to change the performance much. Moreover, > > the row cache ‘size’ according to nodetool was very tiny. Here is a > > snapshot of the nodetool info after running few read tests: > > Key Cache : size 2448 (bytes), capacity 104857584 (bytes), 231 hits, 266 > > requests, 1.000 recent hit rate, 14400 save period in seconds > > Row Cache : size 96 (bytes), capacity 4194304000 (bytes), 9 hits, 13 > > requests, NaN recent hit rate, 0 save period in seconds > >
