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multi-master 'merge' replication


Re: multi-master 'merge' replication Paul Ibison
2/26/2007 12:00:00 AM
sql server replication: Hi Timi,
I'm not too sure what you mean by "multi-master" in your description - merge
operates with a publisher-subscriber setup (although alternative sync
partners cloud the issue slightly) and presumably the active/active cluster
represents the publisher with the subscriber being at a remote site. I
haven't set up the configuration you mention, but I see some issues. The
load balancing will need to be done by a middle-tier (ie not out of the box)
and this is fine, but what I would be concerned about is the conflict
resolution. Do you intend to partition the data accross the 2 merge
replicated databases and have the load-balancer determine which partition is
accessed? If not there will be a strong possibility of conflicting updates.
If this is allowed in the business model then it sounds fine.
Latency/performance in your setup will depend on many factors and I would
recommend testing empirically. Apart from that I'd set up large ranges for
the identity columns as per usual.
Cheers,
Paul Ibison SQL Server MVP, www.replicationanswers.com

Re: multi-master 'merge' replication Paul Ibison
2/26/2007 12:00:00 AM
OK Timi - I think I understand your case but BTW terminologywise
multi-master is not normally a phrase applied to replication, and
bidirectional normally refers to transactional. Also you now mention DR but
originally mention load-balancing, so if it is just DR then my comment about
conflicts being an issue can be disregarded.
For DR, as long as the identity ranges are large and the publication's
retention period and history retention period are both sufficient, then
offline access could continue.
Cheers,
Paul Ibison SQL Server MVP, www.replicationanswers.com

multi-master 'merge' replication Timi
2/26/2007 3:04:03 AM
SQL Live-Live – what are the options for the DB clusters to be in an
ACTIVE/ACTIVE configuration with multi-master “merge” replication? What is
the network requirements, what about data integrity, latency, performance?

Basically I am trying to design a new SQL Database infrastructure to support
our webfarm which spread across two geographically dispersed sites, and
trying to make sure that the data is load balanced across the two sites.
Re: multi-master 'merge' replication Timi
2/26/2007 6:37:07 AM
Hi Paul,
Thank you for your prompt reply,

I at setting up a multi master bidirectional replication scenario where both
servers can work autonomously in case of a DR situation, or planned downtime

[quoted text, click to view]
RE: multi-master 'merge' replication Timi
2/26/2007 8:51:02 AM

Hi Paul
THANKS AGAIN FOR YOUR REPLY

THE SENARIO HAS CHANGE SEE BELOW

SQL Server database load-balancing

a way to load-balance across the SQL Server groups in each data centre to
make failover automatic if a SQL server stops responding

Solution must provide a way for Operations to manually take SQL servers
in/out of the load-balanced group without requiring any action by another
group.

Solutions mustn’t impact performance by >5%



[quoted text, click to view]
Re: multi-master 'merge' replication Paul Ibison
2/26/2007 4:58:55 PM
OK - then the data isn't partitioned in any way and everyone can change
everything. In this case I'd expect the main problem to be one of coping
with conflicts. The load-balancing component could possibly mitigate this by
determining which users to send to which server eg UK users will edit uk
data so they go to the UK merge replicated database, similarly for US users.
When the load-balancing component detects a failed heartbeat, all users go
to the same server.
Cheers,
Paul Ibison SQL Server MVP, www.replicationanswers.com

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