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sql server replication
group:Why mirror when I could replicate?
sql server replication:
Howdy. I was reading PromisedOyster's question on "Replication vs. Mirroring"
and it got me thinking, what would the benefit to Mirroring be in light of the new Replication enhancements? To be clear, Im referring to Peer to Peer Replication, or continuous Replication with Immediate Updating Subscribers. Replication can now do schema changes and immediate stored proc changes, the major reason to not use it for High Availability in previous versions IMO. Plus it can be used for reporting purposes as well, whereas mirroring cannot. Plus failing over, whether manual or automatic, would never even be a consideration as it would always be up and running (of cousres the app would need to be repointed). All this being said, why would I ever want to mirror over using replication? The only possibility I can think of would be licensing issues?
Thanks Hillary, but I still don't even see the benefit to automatic failover.
After all, the app still has to be repointed to the mirror server in the event of failure. If replication were being used this would be just the same. Plus it is already "failed over" as it's always up and running. Thoughts? [quoted text, click to view] "Hilary Cotter" wrote:
> As you noted Mirroring has automatic failover. That is its major selling > point as well as simplicity to set up and maintain. > There are a lot of drawbacks to it. I prefer replication as the risk of data > loss is less than if you are using the high performance mode. In high safety > mode IMHO the latency issues of mirroring make it not a great choice. > > - > Hilary Cotter > > Looking for a SQL Server replication book? > http://www.nwsu.com/0974973602.html > > Looking for a FAQ on Indexing Services/SQL FTS > http://www.indexserverfaq.com > > > > "ChrisR" <ChrisR@discussions.microsoft.com> wrote in message > news:B61697D6-FEA8-4A71-BB32-22EFF0DF72C1@microsoft.com... > > Howdy. I was reading PromisedOyster's question on "Replication vs. > > Mirroring" > > and it got me thinking, what would the benefit to Mirroring be in light of > > the new Replication enhancements? To be clear, Im referring to Peer to > > Peer > > Replication, or continuous Replication with Immediate Updating > > Subscribers. > > Replication can now do schema changes and immediate stored proc changes, > > the > > major reason to not use it for High Availability in previous versions IMO. > > Plus it can be used for reporting purposes as well, whereas mirroring > > cannot. > > Plus failing over, whether manual or automatic, would never even be a > > consideration as it would always be up and running (of cousres the app > > would > > need to be repointed). All this being said, why would I ever want to > > mirror > > over using replication? The only possibility I can think of would be > > licensing issues? > > > > TIA, ChrisR > >
As you noted Mirroring has automatic failover. That is its major selling
point as well as simplicity to set up and maintain. There are a lot of drawbacks to it. I prefer replication as the risk of data loss is less than if you are using the high performance mode. In high safety mode IMHO the latency issues of mirroring make it not a great choice. - Hilary Cotter Looking for a SQL Server replication book? http://www.nwsu.com/0974973602.html Looking for a FAQ on Indexing Services/SQL FTS http://www.indexserverfaq.com [quoted text, click to view] "ChrisR" <ChrisR@discussions.microsoft.com> wrote in message news:B61697D6-FEA8-4A71-BB32-22EFF0DF72C1@microsoft.com... > Howdy. I was reading PromisedOyster's question on "Replication vs. > Mirroring" > and it got me thinking, what would the benefit to Mirroring be in light of > the new Replication enhancements? To be clear, Im referring to Peer to > Peer > Replication, or continuous Replication with Immediate Updating > Subscribers. > Replication can now do schema changes and immediate stored proc changes, > the > major reason to not use it for High Availability in previous versions IMO. > Plus it can be used for reporting purposes as well, whereas mirroring > cannot. > Plus failing over, whether manual or automatic, would never even be a > consideration as it would always be up and running (of cousres the app > would > need to be repointed). All this being said, why would I ever want to > mirror > over using replication? The only possibility I can think of would be > licensing issues? > > TIA, ChrisR
I was unaware of the Client Side Redirect that could be written into the app
in the event of failure. That makes sense, thank you both. [quoted text, click to view] "ChrisR" wrote:
> Howdy. I was reading PromisedOyster's question on "Replication vs. Mirroring" > and it got me thinking, what would the benefit to Mirroring be in light of > the new Replication enhancements? To be clear, Im referring to Peer to Peer > Replication, or continuous Replication with Immediate Updating Subscribers. > Replication can now do schema changes and immediate stored proc changes, the > major reason to not use it for High Availability in previous versions IMO. > Plus it can be used for reporting purposes as well, whereas mirroring cannot. > Plus failing over, whether manual or automatic, would never even be a > consideration as it would always be up and running (of cousres the app would > need to be repointed). All this being said, why would I ever want to mirror > over using replication? The only possibility I can think of would be > licensing issues? >
The connection string has a parameter for failover partner. So if the
principal goes down and the mirror comes online, the app if coded correctly will retry and connect to the mirror. With replication there is a little more work to do to repoint the applications to the subscriber. -- Hilary Cotter Looking for a SQL Server replication book? http://www.nwsu.com/0974973602.html Looking for a FAQ on Indexing Services/SQL FTS http://www.indexserverfaq.com [quoted text, click to view] "ChrisR" <ChrisR@discussions.microsoft.com> wrote in message news:2AAA4737-AEC1-43ED-9E4D-3F72919C1272@microsoft.com... > Thanks Hillary, but I still don't even see the benefit to automatic > failover. > After all, the app still has to be repointed to the mirror server in the > event of failure. If replication were being used this would be just the > same. > Plus it is already "failed over" as it's always up and running. > > Thoughts? > > "Hilary Cotter" wrote: > >> As you noted Mirroring has automatic failover. That is its major selling >> point as well as simplicity to set up and maintain. >> There are a lot of drawbacks to it. I prefer replication as the risk of >> data >> loss is less than if you are using the high performance mode. In high >> safety >> mode IMHO the latency issues of mirroring make it not a great choice. >> >> - >> Hilary Cotter >> >> Looking for a SQL Server replication book? >> http://www.nwsu.com/0974973602.html >> >> Looking for a FAQ on Indexing Services/SQL FTS >> http://www.indexserverfaq.com >> >> >> >> "ChrisR" <ChrisR@discussions.microsoft.com> wrote in message >> news:B61697D6-FEA8-4A71-BB32-22EFF0DF72C1@microsoft.com... >> > Howdy. I was reading PromisedOyster's question on "Replication vs. >> > Mirroring" >> > and it got me thinking, what would the benefit to Mirroring be in light >> > of >> > the new Replication enhancements? To be clear, Im referring to Peer to >> > Peer >> > Replication, or continuous Replication with Immediate Updating >> > Subscribers. >> > Replication can now do schema changes and immediate stored proc >> > changes, >> > the >> > major reason to not use it for High Availability in previous versions >> > IMO. >> > Plus it can be used for reporting purposes as well, whereas mirroring >> > cannot. >> > Plus failing over, whether manual or automatic, would never even be a >> > consideration as it would always be up and running (of cousres the app >> > would >> > need to be repointed). All this being said, why would I ever want to >> > mirror >> > over using replication? The only possibility I can think of would be >> > licensing issues? >> > >> > TIA, ChrisR >> >> >>
Chris,
as far as I know this is not the case - automatic failover is possible in mirroring. There is a modification made to the connection string that enables a client-side redirect so no manual repointing is necessary. Have a look at http://www.microsoft.com/technet/prodtechnol/sql/2005/dbmirror.mspx - "client-side redirect". Cheers, Paul Ibison SQL Server MVP, www.replicationanswers.com
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