Exchange Server Forums

Question What happens when Witness Server of Exchange got down/No connection ?

Users viewing this topic: none

Logged in as: Guest

Printable Version

All Forums >> [Microsoft Exchange 2010] >> General >> Question What happens when Witness Server of Exchange got down/No connection ?

Page: [1]

Message

<< Older Topic Newer Topic >>

Question What happens when Witness Server of Exchange g... - 3.Nov.2011 2:25:23 AM

z_haseeb

Posts: 53
Joined: 5.Sep.2007
Status: offline

OS of Exchange = win2008R2

Exchange Version = 2010

HA = 2nodes in DAG each has one database (Total 2 databases ). CAS/Hub/All roles on each node(No additional Server for CAS/CAS array and HUB Transport)

Domain Controler = one (one win2008)

1.) What happens when Witness Server of Exchange got down/No connection with Witness Server?

2.) May we get email when Witness Server down ?

Post #: 1

Featured Links*

RE: Question What happens when Witness Server of Exchan... - 9.Nov.2011 5:51:12 AM

jveldh

Posts: 2271
Joined: 12.Apr.2008
From: The Netherlands
Status: offline

Hi,

It depends which server contains the file share witness. As this FWS is the quorum the server which contains both will stay online since to "members" of the cluster are online. If this server fails the DAG will go down.

It might be a better option to move the FSW to another server. As long a both DAG members are online but the FSW fails (if hosted on another server) you can continue to receive mail. This since you still have quorum.

Regards,
Johan

_____________________________

Best regards,

Johan Veldhuis

Visit my Exchange blog

(in reply to z_haseeb)

Post #: 2

RE: Question What happens when Witness Server of Exchan... - 10.Nov.2011 11:06:22 AM

ermanishchawla

Posts: 124
Joined: 12.Jul.2011
Status: offline

Your question
OS of Exchange = win2008R2

Exchange Version = 2010

HA = 2nodes in DAG each has one database (Total 2 databases ). CAS/Hub/All roles on each node(No additional Server for CAS/CAS array and HUB Transport)

Domain Controler = one (one win2008)

1.) What happens when Witness Server of Exchange got down/No connection with Witness Server?

2.) May we get email when Witness Server down ?

Answers
This is typical exchange installation when you have two exchange servers running with MB + HT + CAS role and Mailbox are clustered using two members DAG

Now to answer you query I assume the following scenario in your case

Exchange Server 1: Exch01
Exchange server 2: Exch02
Domain Controller: GC01

Now since it is two member DAG, witness is required to build quorum. Now since exchange quorum mechanism is based on majority votes hence following formula is applicable
V/2 + 1 where V= Number of Voters

In your case members of DAG only are voters so you have two Voters hence to build a quorum you need

V/2+1 =2/2+1 =2 Votes

Now let see failure scenario
Exchange Server1=Voter1
Exchange Server2=Voter 2
Domain Controller=Witness Server

Now DAG works with witness server in the sense it places a SMB lock on file located in witness server and then his vote is counted as 2 rather than 1
Assume Exchange Server1 holds a lock on witness server than his vote count is 2
In this case if Exchange Server 2 is down since quorum is maintained and your services are still up( PS : I have assumed both servers in same site)
Now if Exchange server 2 is also up, it cannot place a lock on witness server as it is already locked by exchange server 1 and hence It has only 1 vote but i can connect to Exchange Server 1 so total voters are still 2 for exchange server 2 as well and hence exchange server 2 also can work fine

Now assume Witness Server is down

Exchange Server1=Vote1
Exchange Server2=Vote 2

As long as both are able to talk to each other, quorum is maintained and both can work.

Hence in nutshell
Two members DAG works as longs as two systems are not down

(in reply to z_haseeb)

Post #: 3