shared storage for clustered VMs

I have shared configured storage in pilot environment (Starwind). Shared storage size is 200G and VMware uses 190G of it (for storing VMs and their disks).  I plan on configuring 2 VMs as Microsofr cluster - can I point it to the same 200G shared storage (the one that has been allocated for VMware)?
Or should I create a separate shared storage partion that is separate from the one I use for VMwsre and point microsoft  cluster to it?

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How have you presented the shared storage to your hosts? What are you using...ESX, ESXi? Which version...3.x or 4? Do you have just the 200GB, or do you have other storage space available? How many total VMs do you have? What type of servers will be in the cluster (SQL, Exchg)? You've left out quite a bit of info really to be able to give you the best answer. But, I'll try and share a suggestion...

From what it sounds like, you're just testing things, correct? I'll assume you're using ESX here. (or ESXi) I would split the 200GB into 2 RAID5s, or at least 2 RAID1s (mirrored). I would place VMs on 1 of the RAIDs (datastore), and use the other to create LUNs for more datastore storage or for direct-connected storage to the VMs (RDM - raw device mapping). Microsoft best practices for either Exchg or SQL is to separate DB from Logs. That being said, if you were to configure your storage to be in line with MS best practices, you would have 3 LUNs as a minimum - 1 for VMs, 1 for your DB, and 1 for Logs.

To answer your question about 'pointing the clustered VMs to the shared storage'...well, you actually point your ESX host(s) to the storage. Then, from that storage, you can create VMDKs (volumes), or like I mentioned above, reserve a certain amt of storage to create a couple LUNs for DB and Logging. I really recommend reviewing a couple of VMware's Guides -> ESX Config Guide...chapter on Storage (pg. 89):, and 1 of the SAN Config Guides. Neither may apply but might provide more insight to how shared storage is used in ESX (Fibre and iSCSI SAN Config Guides...use this link for vSphere documentation:

I hope I answered your question. Please let me know otherwise.


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Forgot to the 2nd link for the documentation...there is also a guide on MS CLustering. Another good Guide to look through. :)

If your shared storage is presented to VMware , you can not use that as cluster drive insde MS cluster. You can create a virtual disk and make that shareable between the VMs.
Have a look at this document : for details
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elo-miloAuthor Commented:
"You can create a virtual disk and make that shareable between the VMs. "
----- how do you create a new vmdk disk indeoendant ov VM (so you can point to it later?)
Actually "elo"...I'm not sure what "rvivek" is referring to. I think what he's saying is the VMs can't use a shared "volume" (within the OS).

The vSphere doc link I provided (2nd one), has the MSCS doc within it that resembles "rvivek's". The thing about clustering is, you have to have shared storage that is FC across hosts. The specifics of MSCS are in the Cluster Guide (

elo-miloAuthor Commented:
"you have to have shared storage that is FC across hosts"
----- I noticed that in the doc about MIS Clustering that they say that only Fiber Channel shared storage is not supported, but I though 'not supported' odesn't mean it won;t work. I'll try it in pilot environment with iSCSI shared storage to see if it can be configured.
elo-miloAuthor Commented:
"To answer your question about 'pointing the clustered VMs to the shared storage'...well, you actually point your ESX host(s) to the storage. Then, from that storage, you can create VMDKs (volumes), "
--- how can i create a vmdk volume from available storage? (in order to use it for MS Cluster)?

It depends on your SAN/shared storage infrastructure. I have an EMC SAN, so I'll tell you how I do it for my infrastructure. You'll have to read through your specific SAN infrastructure documentation as well as the doc from the links I provided for explicit answers conducive to your org's setup. In my SAN mgmt console, I create a RAID group (RAID5), then from that RAID group, I can create 1 or several LUNs, depending on what I want to use the storage in that RAID group for. For simplicity's sake, let's just say we create 1 LUN. Then, after that LUN is created, I create a Storage Group and assign ESX/i hosts (2 or more, thus where we get the term 'shared storage') to that group. The hosts need to be connected and added to your SAN first, which is done by some type of SAN switch zoning/configuration. After I add the hosts to the Storage Group I created, I then need to add the LUN I created in the RAID group to that Storage Group the ESX/i hosts are assigned to. After your SAN is all set up, you then go into vCenter to and create a cluster within vCenter. After the cluster is created, you add your ESX/i hosts to that cluster. Then, what you need to do is 'Add Storage' (datastore). But, before you can add that shared storage you just created, you need to do a scan of your HBAs on your hosts so you can 'see' the storage you created in your SAN. Then, 'Add' that storage to your host in vCenter. Each host in the cluster will see that SAN storage.

Hope that helps. What you really need to do from here is read up on VMware technology as well as Clustering. Let me know if I didn't fully answer your question.

elo-miloAuthor Commented:
Excellent answer, thanks.
But I was thinking about something different: When you said: "Then, from that storage, you can create VMDKs (volumes), " I understood it this way:
1. You already have shared storage configured and presented four ESX cluster.
2. This storage is seen on ESX cluster as (let's say) DATASTORE_12
3. The I was thinking that out free spave available on DATASTORE_12 you can take (let's say) 100G of space and turn it into vmdk file.
4. Then when you create MS Cluster from 2 VMs you'll point them to this vmdk file that will their shared cluster storage.
I guess that is not possible....
That isn't possible, if I am reading your steps correctly. Your VMs (C: drive VMDKs) are on shared storage (say, 'Datastore_12). You can create a new Hard Disk in a VM on that same datastore and add it as a volume to one of your VMs and share it. Then, on your 2nd VM, you create a mapped drive to that shared storage you created in your 1st VM.

So, yes, as you stated, that is not possible. :)

Hope that helps.

elo-miloAuthor Commented:
OK, so let me sum it up:

So the only option in my case is (on the very general level)
1. Create space on shared storage
2.  DEDICATE created space to MS Clustering for 2VMs 9this ine gonna be saparete from the storage space used for ESX in order to host VMs)

In a very simplistic way - VMs are hosted on 1 shared storage. But space used for MS clustering between VMs will be located on a separate storage.
Is that correct?
Well, I don't know that you have to dedicate a whole datastore for your Cluster. If you're wanting to configure a true cluster, what you should do is have your VMs on different datastores as well as different hosts. For your data, you can create a VMDK (Hard Disk) for your VMs on which datastore you have space on. For the most part, you're on the right track though.

I believe the Cluster Guide above outlines best practices/suggestions on clustering possibilites/solutions. :)

elo-miloAuthor Commented:
"Well, I don't know that you have to dedicate a whole datastore for your Cluster. "
--- OK, let me put this way in this case - you need to have a separate LUN dedicated to MS clustering between 2 VMs. It cannot be the same LUN where VM files are gosted on. Is that correct?
OK, I see what you're saying (had to re-look at the Guide). So, the correct answer is, it depends. :)  It just depends on how you're going to set up your MS Cluster. Pg. 13 in the Guide gives disk/storage requirements based on the type of Cluster you set up. So, if you have a Cluster where the VMs are on different physical ESX hosts, yes, you are correct.

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