Jim Lawrence
accessd at shaw.ca
Thu Sep 15 07:31:12 CDT 2005
Hi Billy: Very interesting. From your comments I checked out http://www.microsoft.com/technet/prodtechnol/sql/2005/dbmirror.mspx You are right in that the article(s) does not clearly state whether one or two copies of the product are necessary. Jim -----Original Message----- From: dba-sqlserver-bounces at databaseadvisors.com [mailto:dba-sqlserver-bounces at databaseadvisors.com] On Behalf Of Billy Pang Sent: Wednesday, September 14, 2005 11:54 PM To: dba-sqlserver at databaseadvisors.com Subject: Re: [dba-SQLServer] sql server 2005 database mirroring - howmany copies of sql server? Hi Jim: Not sure if it is publishing or subscribing in this scenario. Are you talking about (snapshot) replication? Database mirroring is new in sql server 2005, which is a bit different than replication. in database mirroring, there is a principal database, which is what client accesses. if the principal database is disconnected, the witness tells the mirror server to become the principal server; the failover is automatic and transparent to the client; replication is like database mirroring because there are two copies of the db except that in db mirroring, the client only sees one database. replication probably good for WANs; for db mirroring, it is preferred that all servers are on same domain over standard network infrastructre. Billy >From: Jim Lawrence <accessd at shaw.ca> >Reply-To: dba-sqlserver at databaseadvisors.com >To: dba-sqlserver at databaseadvisors.com >Subject: Re: [dba-SQLServer] sql server 2005 database mirroring - >howmany copies of sql server? >Date: Wed, 14 Sep 2005 22:19:35 -0700 > >Hi Billy: > >Do you mean Publishing and Subscribing? I have setup two versions of SQL >server (2000 Enterprise and 2000 Development) on a couple of computers and >have tested them passing data back and forth... It is quick process, >something like Access synchronizing but at this time it is no more than a >local backup. > >Jim > >-----Original Message----- >From: dba-sqlserver-bounces at databaseadvisors.com >[mailto:dba-sqlserver-bounces at databaseadvisors.com] On Behalf Of Billy Pang >Sent: Wednesday, September 14, 2005 7:58 PM >To: dba-SQLServer at databaseadvisors.com >Subject: [dba-SQLServer] sql server 2005 database mirroring - how many >copies of sql server? > >Hello: > >I need someone to clarify database mirroring for me. How many copies of >sql > >server do I need to configure a database mirroring session involving three >separate servers (that includes a witness server)? > >The scenario is this: in the quorum, there are three servers: the principal >server, the mirror server and the witness server. the principal server has >the original db; the mirror server has a copy of the db on principal >server; > >the witness server watches both the principal server and the mirror server. > >If the principal server goes down, the witness automatically tells the >mirror server to take over as principal server, a process that takes 3 >seconds. > >To establish the mirror session for all three servers, according MS >eLearning course 2938, I perform the following: > >For the principal server's participation in the quorum: >1) from the principal server, I run the alter database statement on the >original db > >For the mirror server's participation in the quorum: >2) from the mirror server, I run the alter database statement on the mirror >db > >For the witness server's participation in the quorum: >3) from the PRINCIPAL server, I run the alter database statement on the >original db > >Given step 3), I can't tell if I need 2 or 3 copies of sql server (ie. do I >need a copy of sql server on the witness server?) Am I missing something >here? > >Thanks in advance, >Billy > > >_______________________________________________ >dba-SQLServer mailing list >dba-SQLServer at databaseadvisors.com >http://databaseadvisors.com/mailman/listinfo/dba-sqlserver >http://www.databaseadvisors.com > >_______________________________________________ >dba-SQLServer mailing list >dba-SQLServer at databaseadvisors.com >http://databaseadvisors.com/mailman/listinfo/dba-sqlserver >http://www.databaseadvisors.com > _______________________________________________ dba-SQLServer mailing list dba-SQLServer at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/dba-sqlserver http://www.databaseadvisors.com