Re: Exchange and GC
- From: Andy David - MVP <adavid@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 12 Oct 2005 09:34:01 -0400
On Tue, 11 Oct 2005 19:48:47 -0700, "Rustom" <RustomNB@xxxxxxxxxxx>
wrote:
>I am receiving conflicting information here...will Exchange automatically be
>able to pick up a GC from another site?
http://www.microsoft.com/technet/prodtechnol/exchange/guides/E2k3TechRef/e0163427-dd90-4761-8f14-8cb41f15939c.mspx
? Global catalog servers Exchange Server 2003 must access global
catalog servers to obtain complete address information for all
recipient objects in the forest. Only global catalog servers contain a
complete replica of all objects in the domain and a partial replica of
all objects in the forest. Global catalog servers that an Exchange
server currently uses are called working global catalog servers.
Almost all Exchange Server 2003 user-context directory service
transactions target global catalogs. Regardless how many global
catalog servers are located in the local Active Directory site, a
maximum of ten global catalog servers can be added to the working
global catalog list. If there are no global catalog servers in the
local site, or if none of the global catalog servers in the local site
pass the suitability tests, then DSAccess uses a maximum of 200
off-site global catalog servers with the lowest costs. Because the
directory service server used for a global catalog is also itself a
domain controller, this server may be used as both types of
directories.
? Domain controllers Domain controllers are used for user-context
requests when the requesting service has sufficient knowledge of the
location of the requested user object in the issued search. These
domain controllers are also called working domain controllers. Working
domain controllers are domain controllers in the local domain that can
accept domain naming-context queries. Regardless of how many domain
controllers are located in the local Active Directory site, a maximum
of ten domain controllers can be added to the working domain
controller list. If there are no domain controllers in the local site,
or if none of the domain controllers in the local site pass the
suitability tests, then DSAccess uses off-site domain controllers with
the lowest costs.
Queries to working domain controllers are load-balanced on a round
robin basis to avoid overloading a single domain controller. If the
working domain controllers are not hard-coded in the registry, the
list of working domain controllers is re-evaluated and re-generated
every 15 minutes using the topology discovery process and suitability
tests.
? Configuration domain controllers Exchange Server 2003 can read
from multiple domain controllers. To avoid conflicts when applying
configuration changes to Active Directory, Exchange Server 2003 writes
its configuration information to a single domain controller, called
the config domain controller. When selecting a config domain
controller from the list of working domain controllers, DSAccess gives
preference to a domain controller over a global catalog server. In
addition, DSAccess preferences a directory server in the local site
before using a directory server in a secondary site.
If the config domain controller becomes unavailable to Exchange Server
2003 for any reason, DSAccess selects another working domain
controller as its config domain controller. Every eight hours,
DSAccess re-evaluates the config domain controller role by running a
set of suitability tests. If the tests are successful, DSAccess
continues to use the same config domain controller. If the tests fail,
DSAccess chooses another domain controller from the list of working
domain controllers as the config domain controller.
The core components of Exchange Server 2003 rely on DSAccess to
provide a current list of Active Directory servers. For example, the
message transfer agent (MTA) routes LDAP queries through the DSAccess
layer to Active Directory. To connect to databases, the store process
uses DSAccess to obtain configuration information from Active
Directory. To route messages, the transport process uses DSAccess to
obtain information about the connector arrangement.
DSAccess updates the list of available global catalogs and domain
controllers as changes in the state of the directory service are
detected. This list can be shared with other directory consumers that
do not use DSAccess as their gateway for accessing the directory
service (for example, DSProxy and other components in System
Attendant). The service that is requesting this list is responsible
for the detection of subsequent directory service state changes.
Note
Unless domain controllers and global catalog servers are hard-coded in
the registry, the list of global catalog servers and domain
controllers is re-evaluated and re-generated every 15 minutes using a
topology discovery process and suitability tests.
>
>
>"Rich Matheisen [MVP]" <richnews@xxxxxxxxxxxxxxxxxxxxx> wrote in message
>news:q2tok11uga57fs286n72mgbb3oigeuekhj@xxxxxxxxxx
>> "Rustom" <RustomNB@xxxxxxxxxxx> wrote:
>>
>>>I had an Exchange question with regards to Global Catalog dependency. If
>>>I
>>>have a single Domain Controller which is a GC in a site with Exchange,
>>>what
>>>will happen if that DC fails? Will Exchange go down, or will it be smart
>>>enough to communicate with another GC in a different pysical location /
>>>site?
>>
>> You'll be in trouble. :)
>>
>> The GC won't be the cause of it, though. Exchange won't find another
>> DC to act as a Configuration DC outside its own site unless you
>> configure it manually.
>>
>> --
>> Rich Matheisen
>> MCSE+I, Exchange MVP
>> MS Exchange FAQ at http://www.swinc.com/resource/exch_faq.htm
>> Don't send mail to this address mailto:h.pott@xxxxxxxxxxxxx
>
.
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