But of the WAN link goes down between site A and site B, and both sites can still talk to the fsw in site C, you could potentially end up with a split brain DAG, which is Very Bad Mojo.
Missy On Oct 26, 2011, at 3:34 PM, "Young, Philip" <philip.yo...@covance.com<mailto:philip.yo...@covance.com>> wrote: Ok apologies to both you and John, I probably didn’t give enough info. My goal is to make sure what is planned works but I was not privy to early design meetings. The design is being proposed by a consultant/architect. I queried it and received the following reply Plan is for 8 member DAG split 4/4 between sites a and b. FSW will be housed in site C. This way if there's a site outage, surviving side will be able to contact FSW. If site a is down/unavailable and sites b and c are both up can quorum not be achieved that way.? Regards Phil ________________________________ From: Michael B. Smith [mailto:mich...@smithcons.com] Sent: 26 October 2011 19:26 To: MS-Exchange Admin Issues Subject: RE: DAG Question The question doesn’t compute. :) The issue, as I believe another poster pointed out, is that reaching quorum is impossible with an even number of live servers that don’t have access to the FSW. The cluster will go offline. Warning: I don’t know your design goals. Based on what little information I have, I would tend to suggest you have two DAGs, keeping the same server distribution. Site A has two servers for DAG-1, site B has two servers for DAG-1, the FSW for site A is in site A. Reverse that for DAG-2 being homed in site B. Regards, Michael B. Smith Consultant and Exchange MVP http://TheEssentialExchange.com From: Young, Philip [mailto:philip.yo...@covance.com] Sent: Wednesday, October 26, 2011 10:41 AM To: MS-Exchange Admin Issues Subject: RE: DAG Question Ok thanks Michael. One reason for posting my question was that I could not find anyone else who had done it this way. I was told the reasoning behind this is that if even if we lost site A we would still have the 3 members in site B plus the fsw in Site C. is that logic flawed? Can you be more specific about what quorum issues we might face? BTW the intention is to have active mailboxes in both sites A and B. we are at the design/test phase so not written in stone yet. Regards Phil ________________________________ From: Michael B. Smith [mailto:mich...@smithcons.com]<mailto:%5bmailto:mich...@smithcons.com%5d> Sent: 26 October 2011 14:48 To: MS-Exchange Admin Issues Subject: RE: DAG Question Yes. That could lead you to having quorum issues. Regards, Michael B. Smith Consultant and Exchange MVP <http://TheEssentialExchange.com>http://TheEssentialExchange.com From: Young, Philip [mailto:philip.yo...@covance.com]<mailto:%5bmailto:philip.yo...@covance.com%5d> Sent: Wednesday, October 26, 2011 9:37 AM To: MS-Exchange Admin Issues Subject: DAG Question We are planning an Exchange 2010 rollout and plan an 8-node DAG with 4 members in Site A and 4 in Site B and the FSW in Site C. Are there any drawbacks with doing it this way? Anybody have any good reasons why we shouldn’t do this? Thanks in advance. 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