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We are planning to place a HP MSA P2000 with two FC/iSCSI controllers in our network.

We have two options to provide more storage to Virtual Machines (We are running Hyper-V):

A) Add iSCSI targets to the Virtual Hosts and then create VHD that we would add to each guest server.

B) Directly add iSCSI targets in each guest server.

Just wondering if one of those options is better than the other, and which is the common practice in a virtualized environment.

Thanks in advance for any input!

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    It might help to know how how many virtual hosts you have. Option A is almost certainly the more flexible option, but you could potentially look at clustered storage for high availability too.
    – john
    Jul 3, 2013 at 16:32

5 Answers 5

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Presenting your iSCSI storage to the virtualization hosts is the most common usage scenario but you may have specific needs and/or requirements for presenting your iSCSI storage to your virtual machines. It's all dependent on your particular deployment.

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I'd say that option A is the most common and would probably be your best bet in this case.

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A. Set up a CSV (CLustered Shared Volume) and you can use Cluster mechanisms, Failover easily.

Exposing ISCSI into the VM's is something you want to only do on Special occasions (high Performance Targets etc.).

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    +1 Exactly. Only option B we run is a SQL server.
    – Chris S
    Jul 3, 2013 at 16:55
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Attaching your SAN to the host allows you to use VHDs for the VMs, which in turn, allows you to use all the features of machine virtualization, including VM snapshots (checkpoints,) VM-level backup, storage migration, etc.

Attaching your SAN to the guest allows you to use the features of the SAN within the guest, including clustering, MPIO DSMs, VSS hardware providers, etc.

Both statements are true regardless of whether you use iSCSI or Fibre Channel as the protocol for your SAN.

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I am using an HP P2000 G3 iSCSI MSA in my W2K8R2 Failover Cluster. The P2000 can do both, it all depends on how you partition it. For my purposes, I created two LUNs, 1 for the Witness disk and one for the Cluster Shared Volume. All my VMs, 15 and growing, are on the CSV. Each VM is configured using fixed VHDs. If I needed to spin up a large database server I would add storage, create another LUN, and use it as a pass-through disk.

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