What is best solution for exchange 2010 redundancy DAG or NeverFail

we currently have an exchange server 2010 sp3 with around 1500 users on it.
this server is virtual
we need to setup some sort of redundancy for our email system
We are currently looking into either setting up a DAG or maybe using Neverfail
Has anyone any thoughts on which is better
if i have 7 databases on our mail server at the minute do i need to buy enterprise exchange for the second exchange DAG member?
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Mahesh SharmaCommented:
Utilize DAG
Refer to these links:




Exchange 2010 Enterprise Edition is not required for DAG members that host 5 or fewer active and passive databases. If you have more than 5 Active + Passive DB's then you would require Enterprise Edition. Check this article from Paul Cunningham:

dougdogAuthor Commented:
so if i have a 2 node dag and have 6 live databases that would mean 12 running on each server 6 active and 6 passive
is that correct?
then i would need enterprise
Sushil SonawaneCommented:
DAG is best soluation. You can buy exchange server enterprise or either standard edition there is no issue but windows server OS you have to buy enterprise edition because cluster only support enterprise windows edition.
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Mahesh SharmaCommented:
Yes, You are correct
dougdogAuthor Commented:
so standard would only really support 4 databases then
2 active 2 passive and 1 not in the dag
Following is a suggestion from Microsoft regarding VM failover and migration if configured for Exchange VM Servers which are part of DAG. You could also run DAG on standard edition but the server OS should Enterprise Edition. This is because DAG utilizes Fail-Over Clustering component of OS which is supported in Enterprise Editions. Here in your scenario, you may not use Standard edition of Exchange because it only supports creation of 5 databases.

From MS Article:
Exchange server virtual machines (including Exchange Mailbox virtual machines that are part of a database availability group, or DAG), may be combined with host-based failover clustering and migration technology, as long as the virtual machines are configured such that they will not save and restore state on disk when moved or taken offline. All failover activity must result in a cold boot when the virtual machine is activated on the target node. All planned migration must either result in shutdown and cold boot, or an online migration that makes use of a technology like Hyper-V Live Migration. Hypervisor migration of virtual machines is supported by the hypervisor vendor; therefore, you must ensure that your hypervisor vendor has tested and supports migration of Exchange virtual machines. Microsoft supports Hyper-V Live Migration of these virtual machines.

dougdogAuthor Commented:
so i cannot use HA within Vsphere
Md. MojahidCommented:
3 or more DAG members are recommended if you go backup-less. But if you still perform a VSS backup of the DBs, two would be sufficient for most SMORGs.

Also note that you now can have the HT and CAS roles installed on a DAG member. This means that you can get a fully redundant solution using only two Exchange 2010 servers compared to the four Exchange servers (two with HT/CAS installed and two CCR cluster nodes) that was required when using Exchange 2007.

In regards to your second question, whether Exchange 2010 can leverage from the new Exchange VSS plug-in or not is still under NDA
dougdogAuthor Commented:
so how eaxtly  does dag work
if i have 6 databases
and 2 dag members
are 6 databases on server 1 and the same 6 databses on server 2 as passive
then id server 1 goes offline server 2 databases become active
Md. MojahidCommented:
Vsphere HA (VMware ESX 4.0.x/5.0.x) is supported on Exchange 2010 SP1 onwards.


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