Re: How many Global Catalog Servers are needed?
- From: "Jorge Silva" <jorgesilva_pt@xxxxxxxxxxx>
- Date: Sun, 30 Jul 2006 18:28:36 +0100
Hi
- First: The GC enables finding directory information regardless of which
domain in the forest contains the data, and provides Universal Group
Membership Information. Applications also use the first (any object in the
forest) Exchange is the prototypical example of this. (Windows 2003 has the
UGMC (Universal Group Membership caching which isn't the same thing as the
GC).
- Second: The GC is only needed when you have DFL (Domain Functional Mode)
in Native Mode or later where Universal security groups are allowed, more
than one domain or if you use any app that needs to contact the GC (Exchange
is an example), if you need to logon with a UPN.
- Third: There's a registry setting "IgnoreGCFailures" that you can use in
particular scenarios to force a particular DC NOT TO CONTACT a GC for
authentication process. If you don't use Universal groups for securing
things then you can enable IgnoreGCFailures which will allow you to log on
even if a GC isn't abailable in a Native mode domain. However, if you have a
single domain there is no reason not to make every DC a GC. Note that even
with IgnoreGCFailures enabled, you could run into cases where a GC is needed
say when trying to logon with a UPN, etc.
- Fourth: Good practices are to have at least one GC per site, even in a
single domain forest, every DC ALREADY holds ALL of the info so making a DC
a GC costs practically nothing.
The above is also true in a SMALL forest with multiple domains.
As forest size increases the penalty for creating a GC (increase
replication, increased storage) increases.
- When Open a GPO console you received that error because by default the
console tries to contact the PDCe.
--
I hope that the information above helps you
Good Luck
Jorge Silva
MCSA
Systems Administrator
"SEgerton" <SEgerton@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:9E2E6350-05B1-4DF8-88DD-C8F91ECE6369@xxxxxxxxxxxxxxxx
I'm new to Active Directory; and I just started testing a new domain I've
been working on. On one particular test, I started having issues that I
believe are related to Global Catalogs. Let me first give an overview of
the
structure of the domain, and the test that I was trying to perform. Then I
will give the errors that I came across.
I have two offices. Office 1 is our production office. Office 2 is for our
Disaster Recovery. In office 1 we have 3 servers. 2 servers are Active
Directory Domain Controllers, and the third server is a member server used
as
a File Server. Both Domain Controllers are both Active Directory
Integrated
DNS Servers. There is a T1 line that connects both Office1 and Office2. In
Office 2, I have the same setup. I joined the first two servers to the
same
domain in Office 1 as Active Directory Domain Controllers. These two
servers
are also Active Directory Integrated DNS servers. The third server in
Office
2 is also a member server used as a File Server. The File Server in Office
2
is only used at the moment for replication of the File Server in Office 1.
For this we are using a third party replication software. This setup was
put
together this way in the event of a disaster and office 1 goes down, users
can go to Office 2 and work.
Here is the test I tried. I turned off both server 1 and server 2 in
Office
1, hoping that Active Directory would still work because of Server 1 and
Server 2 in Office 2. The redundancy is there for the Domain Controllers
and
for DNS. But after the server were down. I tried logging into the domain
on a
pc as a user, and the logon took a long time. At the same time, he got
into
his profile, but I don't think his Group Policies were in affect. Then I
got
an error. I forget what I was doing to generate it, but here it is.
"A Global Catalog cannot be located to retrieve the icons for the
member list. Some icons may not be shown."
Then in Office 2, I went into Users and Computers on Server 1 and tried to
open a Group Policy Object and got this error.
"Domain controller not found for domain.local" The Domain Controller for
Group Policy operations is not available. You may cancel this operation
for
this session or retry using one of the following Domain Controller
choices.
Here are the choices:
-The one with the Operations Master token for the PDC emulator.
-The one used by the Active Directory Snap-ins.
-Use any available Domain Controller.
OK or Cancel.
I Canceled.
Due to these messages, I believe the problem is due to a Redundancy of
Global Catalog Servers. I don't fully understand them. But my
understanding
is that by default, Global Catalog is installed on the first Domain
Controller of a domain. Therefore I didn't install any additional and only
have one. How many should I have for redundancy?
Thanks in advance.
Shannon
.
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