Multiple Path I/O (MPIO) for iSCSI storage

To ensure server to storage path continuity, we usually deploy redundant physical path components, including NICs (for iSCSI) and HBAs (for FC, SCSI etc). In the event that one or more of these components fails, causing the path to fail, multipathing logic uses an alternate path for I/O so that the servers and applications can still access their data.

Each storage vendor may introduce their own Device Specific Module(DSM) solution, such as PowerPath for EMC. If you did not cater for budget to purchase specific vendor MPIO module, Microsoft did introduce a generic DSM free. I tried it on my W2K8 R2 server on Hyper-V VM and Dell-EMC AX4-5i storage using Round Robin to load balance among the four iSCSI paths. If you are also using W2K8, install MPIO as a feature using Server Manager or "Add-WindowsFeature" cmdlet in Server Core.

Click on Administrative Tools -> MPIO and check on "Add Support for iSCSI devices" on the "Discover Multi-Paths" tab. Reboot the server. On Server Core, you may run 

>"mpclaim -r -i -d "MSFT2005iSCSIBusType_0x9""

Invoke iSCSI initiator and connect to the iSCSI targets - make sure that the option "Enable multi-path" is checked. On server core, you may invoke the same initiator using "iscsicpl.exe" command.

Click "Advanced", connect using different path each time. Repeat and rinse for the number of different paths that you have. Click on "Devices" -> "MPIO". And you should the load balancing policy and the multiple paths linking to the Disk devices.

 For a more complete Server Core configuration, see "MPIO with Windows 2008 R2 Server Core and iSCSI".

Storage options for Hyper-V

Found this excellent online resource that discuss various storage options for Hyper-V. This table is particularly useful:

Missing Deployed Printer Node in Windows 2008 GPMC

Windows Server 2003 R2 onwards supports "Printer Deployment with GPO". There is an excellent guide on WindowsNetworking.com that illustrates the step-by-step deployment.

However, if you attempt the same step in W2K8, you will realize a missing "Deployed Printer Node" in the GPO editor. To get it back, add the "RSAT - Print & Document Services Tool" using "Add Features" in the Server Manager as below:



Go back to GPO editor, expand "Computer or User Configuration" (depending whether per-computer or per-user deployment basis), Policies, and Windows Settings as below:

Live Migration on Multi-Site Clustering POC

Earlier in my post, I mentioned about the "Cheapskate Multi-site Cluster for Hyper-V R2 HA". I did a simple POC using low cost host-based replication called "SteelEye Data Keeper" (as compared to SAN replication) to provide asynchronous data replication over the network.

This is my 2-node cluster POC setup using MS Failover Clustering with quorum type "Node and File Share Majority". In this setup, we can afford any one (not two) site failure to provide continuity.


In this Hyper-V cluster, I have a few VMs running on both clusters. Let's do a live migration of one of the VMs called "PrintSrv" from Cluster01 to Cluster 02.



During migration, I continue my RDP session on PrintSrv to ensure that the VM is still up & running while in migration.



After a while, the current node owner is Cluster02. Live migration is complete without any down time.

Failover Clustering Error 80070005

When I run Validation of my test failover clustering on Hyper-V, I get the following error report:

Validate Cluster Network Configuration Validate the cluster networks that would be created for these servers. An error occurred while executing the test. There was an error initializing the network tests. There was an error creating the server side agent (CPrepSrv). Creating an instance of the COM component with CLSID {E1568352-586D-43E4-933F-8E6DC4DE317A} from the IClassFactory failed due to the following error: 80070005.

This was despite the fact that I checked through all network connection & properties. I even made sure that the network binding order were correct on both nodes - the Public network card is at the top, above the Private network card.

This error usually comes when you have cloned VM. To check whether you have duplicate SID on the cloned VM, check out this blog post. To resolve it, sysprep the cloned VM (thanks to Farseeker) and the problem should go away.

According to this post, another smaller possible reason is that your environment is completely Windows 2008 Domain Controller (note: this error still persist even if the forest/domain level is at W2K3)). To resolve this error

1) Login to your domain controller using domain admin rights

2) Click on start -> run> dcomcnfg

3) Expand Component services -> Computers and right click on My Computer and click on properties

4) Go to Default Properties tab

5) Under default impersonation level select impersonate and apply it.

6) reboot your Domain controller and then try validation again.

Note: if your validation still fails. Dis-join machines from domain and rejoin and try again.

Cheapskate Multi-site Cluster for Hyper-V R2 HA

MS W2K8 R2 announces 2 important new HA features for virtualization: (1) new cluster shared volume (CSV) for Hyper-V HA cluster & live migration and (2) multi-site clustering.

Hyper-V R2 cluster support VM HA & live migration using the Cluster Shared Volume (CSV). CSV is still a shared volume between 2 nodes, except that 2 nodes can own the volume concurrently (instead of single node ownership previously). You may have a single large CSV that stores multiple VHDs and load balance the VMs within the cluster. However, the common shared CSV is still the major single point of site failure (imagine a total site outage e.g. earthquake, power, flood etc).

On the other hand, multi-site clustering can solve the above site disaster issue - each server node owns its storage on one site & replication occurs between the differently located storage box. One site is defined as source storage and the other as target storage. It presents a single virtual volume to a pair of cluster. However, CSV does not support replicated volumes. Hence, only node may own this virtual LUN at any one time. Two types of replication exist - host-based and storage-based. Multi-site clustering supports Hyper-V R2. The recommended quorum type for this setup is "Node and File-share (instead of disk) majority" whereby the file share server also carry a vote. For better resiliency, the file share server is recommended to be hosted at the third site.

I found this online demo that used host-based replication solution - a software called "SteelEye Data Keeper Cluster". As compared to expensive SAN replication solution, an advantage of this software is the retrofitting of any existing storage, as it allows mirroring across different storage types & volume e.g. iSCSI to NAS, DAS to iSCSI etc.

Presentation Virtualization is back in Las Vegas

I thought the term "Presentation Virtualization" was dropped since launch of Windows Server 2008 R2, since it was hardly mentioned in any new Microsoft Windows 2008 R2 literature. It was almost used in synonymous with Remote Desktop Services (f.k.s Terminal Services) RemoteApp.

Right now, I'm attending the Virtualization Pro summit 2010 at Las Vegas. Presentation Virtualization is still mentioned by a few MVP speakers, including Sean Deuby. Sean defined Presentation Virtualization as the display being abstracted from the originating processes.