[Openstack] [swift] how to configure NWR policy

Hua ZZ Zhang zhuadl at cn.ibm.com
Tue Dec 11 06:47:04 UTC 2012


Mike,

Thanks for you clarification. I'm interested in how to enable the following
combinations.
for case 1,  can we do it without sending the HTTP head 'X-Newest'?
for case 2,  how to enable it?
   N=3, W=2, R=2 (Strong Consistence Mode)
   N=3, W=3, R=1 (Strict Consistence Mode)

Best Regards,

                                                                             
 Edward Zhang(张华)                                                          
                                                                             
                                                                             
                                                                             
                                                                             
                                                                             
                                                                             
                                                                             
                                                                             





                                                                           
             Michael Barton                                                
             <mike-launchpad at w                                             
             eirdlooking.com>                                           To 
             Sent by:                  Hua ZZ Zhang/China/IBM at IBMCN,       
             palrich at gmail.com                                          cc 
                                       Alex Yang <alex890714 at gmail.com>,   
                                       "openstack at lists.launchpad.net"     
             12/11/2012 02:31          <openstack at lists.launchpad.net>,    
             PM                        Hai HJ Ji/China/IBM at IBMCN           
                                                                   Subject 
                                       Re: [Openstack] [swift] how to      
                                       configure NWR policy                
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




Does any of our documentation say NRW are directly configurable?  It's not
really quite that simple.

N is a property of the cluster, chosen when you build the ring.
W is always a simple majority of N.
R is generally 1 (eventually consisten reads), but the client can request
it be bumped to N (> highly consistent reads) using X-Newest.

But then there's stuff like we provide RYW consistency on default reads,
which can't really be modeled by NRW notation.

- Mike



On Mon, Dec 10, 2012 at 9:47 PM, Hua ZZ Zhang <zhuadl at cn.ibm.com> wrote:
  Alex, that make sense to me.  thanks a lot. :-)

  Best Regards,

                                                                             
       Edward Zhang(张华)                                                    
                                                                             
                                                                             
                                                                             
                                                                             
                                                                             



  Alex Yang ---12/11/2012 11:37:24 AM---Alex Yang <alex890714 at gmail.com>
                                                                           
       Alex Yang <                                                         
       alex890714 at gmail.                                                   
       com>                                                                
                                                                           
                                                                        To 
       12/11/2012 11:37                                                    
       AM                              Hua ZZ Zhang/China/IBM at IBMCN,       
                                                                           
                                                                        cc 
                                                                           
                                       "openstack at lists.launchpad.net" <   
                                       openstack at lists.launchpad.net>, Hai 
                                       HJ Ji/China/IBM at IBMCN               
                                                                           
                                                                   Subject 
                                                                           
                                       Re: [Openstack] [swift] how to      
                                       configure NWR policy                
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           



  Hi, Zhang,
  Just add 'X-Newest: Ture' in the HTTP GET request.


  2012/12/11 Hua ZZ Zhang <zhuadl at cn.ibm.com>
        Hi all,

        I have a question about swift configuration for NWR policy.
        According to some documents of Swift, NWR is configurable. The
        general configuration is: N=3, W=2, R=1 or 2.
        Swift can provide both models of consistency: strong and eventual.
        But I can't find where to configure this option.

        Any suggestion is appreciated!

        Best Regards,

                                                                             
       Edward Zhang(张华)                                                    
       IBM China Software Development                                        
       Lab                                                                   
                                                                             
                                                                             
                                                                             
                                                                             
                                                                             



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