ArcSDE High Availability > DNS Failover & Log Shipping

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12-11-2013 08:36 PM
CoryWilliams
Occasional Contributor II
Hi All,
We currently have Log Shiping setup to protect against system failure... I am wondering if anyone else has used a DNS Alias for their connections (whether it's in conjunction with Log Shipping or not), as a failover to point from a primary SQL Server to a secondary SQL Server?

I'm aware that users would need to clear the DNS Cache, however that's an acceptable limitation.

Kind regards,

Cory
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3 Replies
WilliamCraft
MVP Regular Contributor
What you're describing is something we are considering, which as you probably know requires you to set all MXDs and other connection points to use the DNS entry rather than the primary server host name.  We have also discussed using a load balancer in active-passive mode and using its name in the same way as the use of the DNS entry I just described.  Are edits taking place on your primary?  If so, are edits expected to resume on the secondary or is read-only mode acceptable for the secondary?  If the answer to these is 'yes', you'll need to think heavily about the type of replication you want to achieve and the tools to do it.  RDBMS replication in SQL Server may work best over Esri replication if you have un-versioned data that needs to exist in both places.  Another possibility is hardware-based replication using SAN technology if your organization uses anything like that.
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CoryWilliams
Occasional Contributor II
Hi Crafty,
Cheers for your comments! I'm aware that I'd need to repoint all of my layer files, services, Database Connections, etc... Is a little daunting. (It's basically a full rebuild for my layers and services -- having said that, it could be a nice time to review and clean up some issues).

With regards to editing, it all depends upon how long the DB Server will be offline. If a full system rebuild needs to take place, then the secondary would more than likely take over and we would look to migrate back at a later stage. Else we could

For the replication, we are using Log Shipping, which appears to be supported: (http://downloads.esri.com/support/whitepapers/sde_/J9208_MS_SQL_Standby_Servers.pdf).

I'm looking forward to testing this, as it would be nice to have confidence that I can failover if the primary SQL Server were to fall over.

Has anyone else looked at this solution at all?

Cheers,

Cory
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WilliamCraft
MVP Regular Contributor
Great!  Log shipping is a good option.  Well, we just had a meeting about this very topic this afternoon and decided to go with a load balancer as the point of entry.  In other words, our MXDs and other connection points will use the load balancer name as the host name so that we don't have to re-path or re-point everything in the event of a failover.  All we need to do is switch the load balancer to point to the secondary host rather than the primary.  We'll use a DNS entry for the load balancer so that it has a familiar and easy name to remember.  We use Oracle here and decided to use SAN-based replication as our means to write to the secondary.  I'm looking forward to what others reply with.
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