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Why multiple EVSites????

Created: 21 Apr 2013 • Updated: 24 Apr 2013 | 9 comments
KeirL's picture
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I'm trying to get my head around when I MUST have a single EV Site and when I can choose to have multiple EV Sites.

Is there a good whitepaper on this?

I've been advised to have multiple EV sites when globally dispersed sites are involved due to the potential issues with directory database connectivity and latency etc (Thanks Tony and JW for that one). But I'd like to better understand the criteria that means I MUST have a single site.

eg What if:

            The target exchange sites are in the same Exchange Organisation? 

            There a DAG nodes across the different regions from the same Exchange domain?

            There is a single domain across all regions?

                  Sub question: If customer wants to split Windows domain between regions in the future does that mean separate EV Sites will make this easier

            Customer wants a single point of management?

            Any other reasons that I've not meantioned     (I don't know what I don't know) :o)

kind regards as always


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Rob.Wilcox's picture

You're right that sometimes it's down to connectivity or proximity to archiving targets.  Another things to consider are the site wide settings in EV. If you have a need for granularity on some of those things, then you might need multiple sites.

Eg If you have high connectivity between say London and Stockholm, then them being in the same site might be fine.  Consider the PST Holding Area ..... if you want local holding areas for London and Stockholm, then one way that this can be achieved is to have 2 sites, even though the two locations are still highly connected.

KeirL's picture

Thanks Rob

So what I'm mainly understanding is that the only real consideration for EVsite design is around latancy and that Exchange architecture has no influence?

That's a good point about the PST holding area's that may mean that two sites are better than one, even if connectivity is good, but I'm concerned about falling into a trap around the exchange architecture which means that my EVsite design is inappropriate.

for example - If we take the London - Stockholm scenario with a single exchange environment consisting of a 4 node DAG (2 nodes per region) and I've configured this a two seperate EVsites (with separate directory databases), and a mailbox databases is failed over from a London node to a Stockholm node how will EV continue to archive and recall archived items for a user whose mailbox is now hosted on an exchange server within a different EVsite?

kind regards


KeirL's picture

Hi Rob

Sorry - that probably wasn't a good example of an exchange architecture consideration that would mean a single site is the ONLY option - as that's a bit obvious....... having said that..... would there be ways around how such a configuration could be done across evsites?

And are there other Architectual considerations that would mean a single site is the ONLY supported method of installing EV?

thanks again

Rob.Wilcox's picture

Well if you really want to, any environment with >1 EV server *can* be multiple sites.

EV will archive across remote locations, it's just less efficient. So if you have 2 DAG members 'local' and 2 DAG members remote, but they're all in the same target domain, then EV will still talk to them, it's just going to be slower.

KeirL's picture

Thanks for your input here....and so just to make sure I've got the right end of the stick here....

If I have to geographical locations with 2 DAG members in each location and all the bandwidth is being consumed by other appliactions (eg not much available for EV) I would place an EVserver on each location to archive the local exchange targets.........

But if I also have concerns over connectivity to the directory database (as this will exist at only 1 site), then I can set up these two EV servers within their own EVsites so each will have a local directory database to communicate with. 

Can you talk me through what would happen if a database failed in geo one and was brought on-line on a DAG member on the remote site..... would the user still be able to archive and restore emails?

many thanks

Rob.Wilcox's picture

I haven't done a dual site setup in a while... so I am not sure about the dual directory database situation that you described. It would be worth checking before committing to the design decision.

Regarding Exchange DAG failover. If I remember correctly then EV will continue to be able to archive from that mailbox database, as soon as it is available on one of the other Exchange servers in the DAG. Of course if that takes 5 minutes, then it'll take EV 5 minutes too. I believe provisioning will need to run in order to fully update EV, but, archiving can/will continue.

MMcCr's picture

Having multiple EV sites will still use one central EV Directory so one of the locations would still need to read/write over the WAN.

As well as the reasons Rob has mentioned, one of the key things for seperate sites is to ensure that Policies and Resources are kept seperate, for example to keep two totally different parts of a company or seperate companies apart and ensure there's minimal risk of policies from one being assigned to data for the other.  If using Building blocks it keeps the 'DR' servers seperate so you can USL over to the other servers on one site and not impact the other, similar for backups, you can put each site into backup mode singly if that how you do it.

Other reasons I've used it are to keep Compliance and user archiving seperated, again to ensure nothing done in one site impacts the other etc.

The key thing sites don't do is allow you to upgrade each site seperately - its the same Directory so you have to upgrade the whole directory, if that would be a problem look at seperate directories.

MMcCr's picture

FYI - for clarity the above is when the EV Site belongs to the same Directory :-), different obviously if they're on different directories.

KeirL's picture

Thanks - yes, I assumed that what you meant.

I also assume that if they were on different directories the above simply wouldn't work.