Unity DC-GC reconnect question

[fn3247]

Quick question, when tweaking DC\GC settings, or trying to get Unity to "failback" to closer DC or GC that has gone offline but is available again, does Unity have to be restarted? Can it be manually forced without a full restart? Can it be made to automatically "failback" to a more preferred DC\GC when those boxes come back?

Situation: we have an AD site which lost it's two preferred GC's, Unity failed to a third GC at another site as it should have. However, there does not seem to be a way I can discern to get Unity to come back to the preferred DC\GC machines without restarting.

Do I have this right?

[kechambe]

There is no failback logic for the DC/GC reconnect functionality. Even if you restart the AvDSAD/AvDsGlobalCatalog services Unity will not switch to a new DC/GC. It takes actual failure or manual intervention to switch DC/GCs.

We don’t have failback logic because full synchs can take very long to complete depending on the size of the directory. This is also why we want 30 minutes of unavailable before we failover.

I also really want to caution against having Unity failover to a DC/GC in another site. It's not supported design for Unity to synch with a DC/GC across a WAN for a number of reasons. Unity will continue to take calls and function as normal even if we can't synch with a DC/GC. Basically all you lose is move/add/change functionality during the outage. The default settings I developed for the DC/GC reconnect feature really are the best setting to entire high availability and proper functionality.

In your situation it makes sense to allow Unity to only reconnect within the same site. Loosing to DC/GCs in the same site at once was probably caused by procedural error or design issues which can probably be addressed and avoided moving forward. If you can correct whatever caused the outage and restrict the scope you’ll have a supported design and shouldn’t have to worry about the DC/GC reconnect feature.

Hope this helps...

Thanks,

Keith

[fn3247]

This does help with the understanding of how this should be made to work.

A follow-on question then... if an organization has multiple sites, and each of those AD sites are configured with local primary/secondary DC\GCs and remote DC/GCs for tertiary use (and beyond) would the recommendation be to really disable the "automatic" find feature and enforce a manual configuration instead?

This has some drawbacks of its own of course, and while I agree that losing both local machines in the above scenario should be unusual, sometimes the teams that run AD environments don't understand the implications during things like upgrades and whatnot. (which is close to what happened here)

Appreciate your perspective.

[kechambe]

The automatic reconnect functionality uses the DsGetDcName function to find a new DC/GC:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/ad/ad/dsgetdcname.asp

By default Unity will get the name of the AD site it is in and pass it in as the 'SiteName' when it requests a new DC/GC. This will ensure that we only get another DC/GC in the same site.

Of course this assumes that AD sites have actually be setup and setup correctly. If an organization doesn't do this then DsGetDcName could return a DC/GC in another site. It also assumes that someone hasn't gone in to the DC/GC Reconnect tool and set 'Allow Unity to search all sites when finding a new DC/GC'.

So you might want to check your settings in DC/GC reconnect. If 'Allow Unity to search all sites when finding a new DC/GC' it not checked then you might want to run this by the AD team and ask them to determine why DsGetDcName returned a DC/GC in another site.

Thanks,

Keith