Global Catalog

Wanted to get specific information on the Global catalog.

When does it replicate? Does it replicate full data
everytime or just the changes? Is there a matrix to
figure how much data is replicated?

We are moving to 3 sites with 2 DCs at each site, does it
make since to place the Global Catalog on all six servers?
or just one DC at each site and turn on casheing?

Hi Sean,

Thanks for your posting here.

I would like to reply to each point in line:

When does it replicate?

A: GC replication is a part of normal Active Directory replication. So it
is based on your scheduled time inter-site.

Does it replicate full data every time or just the changes?

A: In Windows 2000 forests, extending the partial attribute set causes a
full synchronization of all object attributes stored in the global catalog
(for all domains in the forest). In a large, multi-domain forest, this
synchronization can cause significant network traffic. Between domain
controllers enabled as global catalogs that are running Windows Server
2003, only the newly added attribute is replicated.

Is there a matrix to figure how much data is replicated?

A: I recommend that you try capture network performance log to log to
monitor the replication data.

If you get any problem about GC replication, you can enable Active
Directory Diagnostic Event Logging for troubleshooting.

314980 HOW TO: Configure Active Directory Diagnostic Event Logging in
Windows
http://support.microsoft.com/?id=314980

We are moving to 3 sites with 2 DCs at each site, does it make since to
place the Global Catalog on all six servers?
or just one DC at each site and turn on casheing?

A: In general, we recommend that each site contains a global catalog. If
there are too many GCs, the synchronization can cause significant network
traffic.

More information
======
Understanding the global catalog
http://www.microsoft.com/technet/tre...hnet/prodtechn
ol/windowsserver2003/proddocs/entserver/n_gc.asp

244368 How to Optimize Active Directory Replication in a Large Network
http://support.microsoft.com/?id=244368

199174 Directory Replication Basics for Windows 2000
http://support.microsoft.com/?id=199174

248717 How to Modify Attributes That Replicate to the Global Catalog
http://support.microsoft.com/?id=248717

Global Catalog Attributes and Replication Properties
http://support.microsoft.com/?kbid=232517

In addition, the <Windows 2000 Server Distributed Systems Guide> that is
included with the Microsoft Windows 2000 Server Resource Kit, provides more
detail in chapter 6, "Active Directory Replication."

Best regards,
Bob Qin
Product Support Services
Microsoft Corporation

Get Secure! - www.microsoft.com/security

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"Sean Connery" <(E-Mail Removed)> wrote in message
news:886701c3e9f3$7d994fb0$(E-Mail Removed)...
> We are moving to 3 sites with 2 DCs at each site, does it
> make since to place the Global Catalog on all six servers?

Bob gave some good info on the other stuff, but I just wanted to
comment on this part. It is typically intended that you only have one
CG per domain. You can have more but they can cause excess traffic at
replication time. In my case, I only have two DCs so I put it on both
and also run duplicate services on both (DNS, WINS, DHCP <with
different address pools>) so that If I ever have to take one down
there is very little disruption,...there is usually only a breif
"hiccup" when the client renews the DHCP lease and they have to go to
the other DHCP server.


--

Phillip Windell [CCNA, MVP, MCP]
WAND-TV (ABC Affiliate)
www.wandtv.com