I read http://technet.microsoft.com/en-us/library/aa996719.aspx,"Hardware virtualization" and are left with a few questions about it and my correct understanding. 1. Exchange 2010 Server with mailbox role runs as virtual machine on Hyper-V physical host. Configuration: system drive (C:) VHD, iSCSI data drive (E:\Exchdata) , iSCSI log drive (F:\Exchlog). iSCSI network is part of the virtual network and the iSCSI intitiator is running on the virtual exchange server. I understand this is a supported configuration for a Exchange mailbox server and DAG. I read that the data and log drives need to be of fixed size but was not sure if in above configuration the (C:) drive needs to be a fixed size VHD as well. Question: Can the system drive (C:) be a dynamically expanding VHD or is a fixed size VHD required. 2. Placing the above machine on a HA Hyper-V cluster is not supported because of the use of DAG for the mailbox store. Per Microsoft the use of DAG requires the Exchange mailbox server to run on a non clustered Hyper V host (root) or even physical machine. Question: Can I run the above Exchange 2010 mailbox server with DAG on a node of an existing Hyper-V cluster when placing the virtual machine not on a CSV? I.e making it not a highly available service or application? In this scenario the vhd for the Exchange mailbox server would be on a local storage device for that node and this storage is not cluster storage. So at the "root" the Hyper-V host would not be a cluster and DAG could run? Appreciate any experts advise.Gerhard Waterkamp ACSLA Inc.

1. What are you connecting an iSCSI initiator to that wouldn't be a fixed-size disk? Generally it is recommended to dedicate physical drives to Exchange mailbox servers, but you didn't tell us how many mailboxes you'd be supporting. Such rules can often be relaxed for small servers. 2. My interpretation of Microsoft's support position (http://technet.microsoft.com/en-us/library/aa996719.aspx) is that what you want to do is not supported. You are welcome to come to your own conclusion.Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

There’s no official restriction to use dynamic VHD on the OS disk, but dynamic disk isn’t usually a recommended option Dynamic virtual hard disks are not recommended for virtual machines that run server workloads in a production environment Agree with Ed. Based on the words in the article, I don’t think you can use both clustering after put virtual machine on CSV “DAGs are supported in hardware virtualization environments provided that the virtualization environment doesn't employ clustered root servers, or the clustered root servers have been configured to never failover or automatically move mailbox servers that are members of a DAG to another root server” Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

You can most certainly put your Exchange servers in a DAG on a Hyper-V cluster environment. You are correct in that you cannot put the databases into VHDs on CSVs. Theres nothing to stop you putting the VHDs into normal LUNs because you know that, should the parent die, the child systems will also die and application HA will kick in. Obviously you will have the other DAG nodes on other parents. You are using the DAG and not the Hypervisor as HA. Happy happy and, subject to contradiction, supported. Dont use dynamic VHDs though. Use fixed VHDs and thin provision them on the storage, assuming you have such a capability. If you dont have such a capability you obviously have to provide the right amount of disk up-front so using a dynamic VHD makes no sense. The competition, vSphere, happily lets you set an ESX cluster up and specify guests that cannot be VMotioned to other hosts. This is how they permit and support DAG members in an ESX cluster. "GerhardW" wrote in message news:3e965248-9b4a-4c31-8371-b22821bf7574... I read http://technet.microsoft.com/en-us/library/aa996719.aspx,"Hardware virtualization" and are left with a few questions about it and my correct understanding. 1. Exchange 2010 Server with mailbox role runs as virtual machine on Hyper-V physical host. Configuration: system drive (C:) VHD, iSCSI data drive (E:\Exchdata) , iSCSI log drive (F:\Exchlog). iSCSI network is part of the virtual network and the iSCSI intitiator is running on the virtual exchange server. I understand this is a supported configuration for a Exchange mailbox server and DAG. I read that the data and log drives need to be of fixed size but was not sure if in above configuration the (C:) drive needs to be a fixed size VHD as well. Question: Can the system drive (C:) be a dynamically expanding VHD or is a fixed size VHD required. 2. Placing the above machine on a HA Hyper-V cluster is not supported because of the use of DAG for the mailbox store. Per Microsoft the use of DAG requires the Exchange mailbox server to run on a non clustered Hyper V host (root) or even physical machine. Question: Can I run the above Exchange 2010 mailbox server with DAG on a node of an existing Hyper-V cluster when placing the virtual machine not on a CSV? I.e making it not a highly available service or application? In this scenario the vhd for the Exchange mailbox server would be on a local storage device for that node and this storage is not cluster storage. So at the "root" the Hyper-V host would not be a cluster and DAG could run? Appreciate any experts advise. Gerhard Waterkamp ACSLA Inc. Mark Arnold, Exchange MVP.

It is a realativley small server with a couple of hundred mailboxes. Well, the data (e:) and log (f:) volumes connected with iSCSI are of course static discs nothing dynamic there. They are mounted in the virtual machine itself using the iSCSI virtual network. That shouldn't be a problem at all. The system volume (C:) is a vhd as the whole server is a virtual machine. By default when creating a virtual machine it is a dynamically expanding disk. It appears this should be made a static disk in a production environment. If the virtual machine is not part of the HA cluster, I think this is very supported. Gerhard Waterkamp ACSLA Inc.

Thanks all for your answers and comments. I appreciate you taking the time.Gerhard Waterkamp ACSLA Inc.