Read latency depends on many factors, don't forget "physics". If it meets your requirements, it is good.
-----Original Message----- From: Artur Kronenberg [mailto:artur.kronenb...@openmarket.com] Sent: Friday, October 18, 2013 1:03 PM To: user@cassandra.apache.org Subject: Re: Sorting keys for batch reads to minimize seeks Hi, Thanks for your reply. Our latency currently is 23.618ms. However I simply read that off one node just now while it wasn't under a load test. I am going to be able to get a better number after the next test run. What is a good value for read latency? On 18/10/13 08:31, Viktor Jevdokimov wrote: > The only thing you may win - avoid unnecessary network hops if: > - request sorted keys (by token) from appropriate replica with > ConsistencyLevel.ONE and "dynamic_snitch: false". > - nodes has the same load > - replica not doing GC, and GC pauses are much higher than internode > communication. > > For multiple keys request C* will do multiple single key reads, except for > range scan requests, where only starting key and batch size is used in > request. > > Consider multiple key request as a slow request by design, try to model your > data for low latency single key requests. > > So, what latencies do you want to achieve? > > > > Best regards / Pagarbiai > > Viktor Jevdokimov > Senior Developer > > Email: viktor.jevdoki...@adform.com > Phone: +370 5 212 3063 > Fax: +370 5 261 0453 > > J. Jasinskio 16C, > LT-03163 Vilnius, > Lithuania > > > > Disclaimer: The information contained in this message and attachments > is intended solely for the attention and use of the named addressee > and may be confidential. If you are not the intended recipient, you > are reminded that the information remains the property of the sender. > You must not use, disclose, distribute, copy, print or rely on this > e-mail. If you have received this message in error, please contact the > sender immediately and irrevocably delete this message and any > copies.-----Original Message----- > From: Artur Kronenberg [mailto:artur.kronenb...@openmarket.com] > Sent: Thursday, October 17, 2013 7:40 PM > To: user@cassandra.apache.org > Subject: Sorting keys for batch reads to minimize seeks > > Hi, > > I am looking to somehow increase read performance on cassandra. We are still > playing with configurations but I was thinking if there would be solutions in > software that might help us speed up our read performance. > > E.g. one idea, not sure how sane that is, was to sort read-batches by > row-keys before submitting them to cassandra. The idea is that row-keys > should be closer together on the physical disk and therefor this may minimize > the amount of random seeks we have to do when querying say 1000 entries from > cassandra. Does that make any sense? > > Is there anything else that we can do in software to improve performance? > Like specific batch sizes for reads? We are using the astyanax library to > access cassandra. > > Thanks! > >
