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AskSQLTeam
Ask SQLTeam Question
0 Posts |
 Posted - 2006-04-18 : 11:00:34
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| Greg writes "I have a customer who likes my SQLServer2000-based product. They are going to deploy it with failover and redundancy, in mind. Unfortunately, their plan seems flawed. I don't speak the "language" of SQL replication very well, so its hard for me to tell them whats wrong with their plan. I am hoping one of you SQL replication experts can help me:Here's their plan:1) The customer has 3 datacenters, spread across the country. They use round-robin DNS, so that web service requests can hit any one of the web servers. 2) Each web server talks to a SQL Server database within each datacenter.3) They said that they were going to "turn-on" SQL replication in such a way as to synchronize all the databases with each other. In this way, they believe, they achieve high-availability and redundancy.They seem to believe that, in SQL replication, all the databases are constantly talking to each other, making sure everyone in the cluster has the latest database modifications.My limited understanding and research indicates that you can't do this. There can be only one master. Can a SQL Server be both publisher and subscriber to a mirror of itself? Is this kind of active-active-mirroring possible in real-time?Thank you for your help." |
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Krankensteins
Starting Member
24 Posts |
Posted - 2006-04-18 : 14:09:32
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| Thet is inpossible replication works on transathion LOG not on EVENT if You will changes instantly meaded on all servers then thet must suporth application! If thet is posible (changing application) then MS DTC is thet who can help. Only Oracle on DB level suports thet tehnology(RAC active node Clusters) but in one room or with wery high costs interconects. If customer will HA technlogy across country then they need in evry point disk storage with disk replication techology (like Veritas True Copy), but only one node can be active (thet is very expensive technology, but HA, BUT THEAR ISN'T LOGICAL DATA PROTECT )! |
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jen
Master Smack Fu Yak Hacker
4110 Posts |
Posted - 2006-04-19 : 02:14:42
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| i believe they're talking about merge replicationserverA<---->distributor<----->serverB--------------------keeping it simple... |
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Krankensteins
Starting Member
24 Posts |
Posted - 2006-04-19 : 02:58:48
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| If replication works on transaction log then Transation log record is readi for replication after COMIT. If comit hepends on serverA and link with serverB is broken then transaction isn't rooled beck on serverA, but waiting while becomes up and wil be replicated. If DNS on nexst sesion will take ather (serverB) WEB server then [???...???]. |
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mmarovic
Aged Yak Warrior
518 Posts |
Posted - 2006-04-19 : 03:18:15
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| There is an interesting solution for this problem I saw implemented. Each web server writes in a log table. Log table changes are distributed to a few subscribers where stored procedure is executed to store changes in a few tables. When web application selects data it does it from the subscribers. |
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Krankensteins
Starting Member
24 Posts |
Posted - 2006-04-19 : 04:28:41
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| Sou works MS SQL Replication! Diferently LOG Shiping Subscribers Databases stays Online. In Log Shiping in Load status. I think they need Distributed transactions who mades changes in all databases in one block of select. Like F1 Help Exsample :USE pubsGOBEGIN DISTRIBUTED TRANSACTION--LocalUPDATE authors SET au_lname = 'McDonald' WHERE au_id = '409-56-7008'--Remonte EXECUTE remote.pubs.dbo.changeauth_lname '409-56-7008','McDonald'COMMIT TRANGOTher changes becames on local server and on remote server. |
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load balancing and active-active mirroring