Thanks guys. Aaron, I am confused about this. from wiki http://wiki.apache.org/cassandra/ReadRepair, looks for any consistency level. Read Repair will be done either before or after responding data.
>Read Repair does not run at CL ONE Daning On Wed, May 23, 2012 at 3:51 AM, Viktor Jevdokimov < viktor.jevdoki...@adform.com> wrote: > > When RF == number of nodes, and you read at CL ONE you will always be > reading locally.**** > > “always be reading locally” – only if Dynamic Snitch is “off”. With > dynamic snitch “on” request may be redirected to other node, which may > introduce latency spikes.**** > > ** ** > > ** ** > > > 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-01112 Vilnius, Lithuania > Follow us on Twitter: @adforminsider <http://twitter.com/#!/adforminsider> > What is Adform: watch this short video <http://vimeo.com/adform/display> > [image: Adform News] <http://www.adform.com> > > 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. > > *From:* aaron morton [mailto:aa...@thelastpickle.com] > *Sent:* Wednesday, May 23, 2012 13:00 > *To:* user@cassandra.apache.org > *Subject:* Re: Replication factor**** > > ** ** > > RF is normally adjusted to modify availability (see > http://thelastpickle.com/2011/06/13/Down-For-Me/)**** > > ** ** > > for example, if I have 4 nodes cluster in one data center, how can RF=2 vs > RF=4 affect read performance? If consistency level is ONE, looks reading > does not need to go to another hop to get data if RF=4, but it would do > more work on read repair in the background.**** > > Read Repair does not run at CL ONE.**** > > When RF == number of nodes, and you read at CL ONE you will always be > reading locally. But with a low consistency.**** > > If you read with QUORUM when RF == number of nodes you will still get some > performance benefit from the data being read locally.**** > > ** ** > > Cheers**** > > ** ** > > ** ** > > -----------------**** > > Aaron Morton**** > > Freelance Developer**** > > @aaronmorton**** > > http://www.thelastpickle.com**** > > ** ** > > On 23/05/2012, at 9:34 AM, Daning Wang wrote:**** > > > > **** > > Hello, > > What is the pros and cons to choose different number of replication factor > in term of performance? if space is not a concern. > > for example, if I have 4 nodes cluster in one data center, how can RF=2 vs > RF=4 affect read performance? If consistency level is ONE, looks reading > does not need to go to another hop to get data if RF=4, but it would do > more work on read repair in the background. > > Can you share some insights about this? > > Thanks in advance, > > Daning **** > > ** ** >
<<signature-logo7789.png>>
