Fundamental CAS question for Exchange 2010 and 2007 Co-existence...

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M

Millardus

Hi everyone,

A colleague of mine came back from an Exchange 2010 Design course and claims that he was informed a CAS2010 Server can talk directly to a Exchange 2007 mailbox server.. I am fairly sure this is incorrect.. I believe it still works via a proxy or redirect to the CAS2007 server which then talks directly to the 2007 mailbox server. I am correct?

I have a couple of other questions if I may:

1.) I assume that Redirection or proxying from 2010CAS to 2007CAS is the case with all incoming connections...Outlook anywhere, ActiveSync, POP, IMAP...... ?

2.) If a 2010CAs definitely cannot talk directly to a 2007 Mailbox Server, then this suggests I will have to run my existing bank of 12*2007 CAS servers, alongside a bank of 2010*CAS servers during migration... I'm pretty sure I will be asked to minimise the number of 2010 CAS servers I need for the initial stages of migration however(due to load on ESX). Does anyone have any anecdotal " thoughts" as to whether a 2010 CAS which is doing " mostly" redirection will be under as much load as a 2007 CAS that is actually handling these connections?

I run a 50 000 mailbox environment which has ALL of its connections via Outlook Anywhere, IMAP or POP. We have NO direct Mapi connections so even for 2007 our CAS servers take a beating.

Any ideas would be appreciated guys

Tom
 
S

Steve Goodman

Hi Tom,

1) Yes, you are mostly correct. Exchange 2010 CAS doesn't talk directly to the Exchange 2007 mailbox servers - except for Outlook Anywhere which does use the RPC Proxy to proxy the client request direct to Exchange 2007 mailbox servers.

2) If the majority of your traffic is Outlook Anywhere then you will see load on the new CAS servers, if it's OWA, IMAP or POP then it will be redirected/proxies, the first of which won't have a noticeable effect.

Steve

Steve Goodman
Check out my Blog for more Exchange info or find me on Twitter
 
B

Brian Day MCITP

There are other times when 2010 CAS talks to 2007 Mailbox like EAS when the device doesn't support Autodiscover.

Please see this article to understand proxying and redirection in Exchange 2010 and under what circumstances each is used.

http://technet.microsoft.com/en-us/library/bb310763.aspx

Microsoft Premier Field Engineer, Exchange
MCSA 2000/2003, CCNA
MCITP: Enterprise Messaging Administrator 2010
Former Microsoft MVP, Exchange Server
My posts are provided "AS IS" with no guarantees, no warranties, and they confer no rights.
 
M

Millardus

Thank you Brian and Steve. Good to get some grounding there.

Tom
 
M

Millardus

Ooops, I was going to make 2 more addition to my questions. I hope you don't mind....

It is looking likely, for budgetary reasons more than anything, that if I do go ahead with Exchange 2010 deployment in 2011, it will be for an extended period of co-existence. To my mind, this looks like I will need to be running a large set of both Exchange 2007 and Exchange 2010 CAS servers.... Am I " basically" correct in this assumption?

Secondly, and I believe the answer is yes, is it NOT recommended to run in co-existence for an extended period? Or is there no " real" issue with doing this? I may be talking about 18-24 months of co-existence where there could be a 25000\25000 split of users....

Tom
 
G

Gavin-Zhang

Hi Millardus,
Q1:
In my opinion, maybe you do not need a large set of exchange 2010 servers in the coexistence.
Some suggestion for you:
1. I would deploy one cas exchange 2010 cas server or more, but not need cas servers as many as exchange 2007, and then create a CAS array, if we need more CAS server, we just add new cas into the CAS array.
2. If you have several sites, it would need more CAS servers, at least, need one in each site.
Q2:
If you want to keep the coexistence for a long period, you could do that, there is no issue with it, it depends the migration schedule.
Some information for you:
http://technet.microsoft.com/en-us/library/dd638158.aspx
http://technet.microsoft.com/en-us/library/ff805041.aspx
http://technet.microsoft.com/en-us/exdeploy2010/default.aspx#Home
Regards!
Gavin
 
B

Brian Day MCITP

While both systems can live alongside each other for as long as necessary, you'll be dealing with knowing/supporting two side-by-side systems. This means 2 DR plans, 2 backup/restore plans, 2 of basically everything. :) We would recommend you migrate to 2010 as soon as your business allows simply to avoid managing two seperate systems and so that your users can all benefit from the improvements in 2010.Microsoft Premier Field Engineer, Exchange
MCSA 2000/2003, CCNA
MCITP: Enterprise Messaging Administrator 2010
Former Microsoft MVP, Exchange Server
My posts are provided "AS IS" with no guarantees, no warranties, and they confer no rights.
 
M

Millardus

Thanks Gavin\Brian

I am multisite, but we only have one namespace as our external switches support load-balancing of incoming connections, so I would need a CAS2010 array indeed but that is simple enough.

My main area of concern (Which I am tempted to get Consultancy advice on) is in sizing the CAS and subsequently the ESX requirements for additional CAS2010 servers and 2010 Hub Transport servers. Sizing the 2010 mailbox and storage I have pretty much got clear in my head.

Our ESX environment run everything apart from the mailbox nodes. We have 12*2007 CAS servers on there to handle a massive IMAP load, Outlook Anywhere load and OWA load (ALL our connections fall into 1 of these 3 types). We also have 4 Hub Transport server....no Edge servers or Unified Messaging deployed. We have NO direct MAPI connections...effectively we work a little bit like an ISP to our Academic userbase.

My ESX environment is also running other services (SharePoint for instance, Blackberry) and though it is meant to be a resilient configuration, I currently cannot run ALL VM's on half the number of ESX servers I have. The addition of further CAS2010 and Hub tranport 2010 servers for an extended co-existence period is going to cost me in ESX servers....the question is how many. At some point I would need to divert all incoming traffic to the Exchange 2010 Array....but I have as yet not figured out how much load these 2010 CAS servers will experience... I know that they redirect IMAP, POP, OWA connections to CAS 2007 servers, but that they DO handle Outlook Anywhere connections for both 2010 and 2007 mailbox servers.... As well as Activesync under the correct cicumstances.

So the challenge I am posed with is HOW many CAS2010 Servers will it take to handle all the incoming traffic, knowing that initially CAS2010 will offload most of it to my large CAS2007 Array....

I certainly dont want co-existence to run for 18-24 months, we are a small team so managing 2 systems definitely does not appeal.
 
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