Is it possible to share iSCSI disk space between multiple VM's?

We are running VMWare ESXi 3.5 on a Dell PowerEdge 1850 and an EMC/Dell AX150i SAN box.

I have various test VM's running and am happy to move to the next stage and go live with "grown up" servers but I would like multiple VM's to be able to see the same disk space.

Is it possible to create a Datastore and then allow more than one VM to see it? If so how? as I am now very confused.

We are using VMware Infrastructure Client and in the Storage Adapters I can see the LUN as vmbha32:0:2, LUN ID 2,

If I now go to Storage and click on Add storage, I get the option of a Disk/LUN or Network File System and from here I am stuck.

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Unfortunately, there is not different way to do what you're wanting in the virtual realm that you do in the physical. But, that being said, let me share at least what my line of thinking was above and see if it's something you can use...

First, and I don't think it really would fit for your org, but what I was thinking is just have your central file storage server VM and do 1 of 2 things:
- Backup the VM using Veeam or,
- Replicate it
As far as the data goes, you would have that on your SAN and connect it to your file storage VM as a RDM connection. You then backup your data as normal. If your file storage VM crashes, if you have a b/u of your VM, you use Veeam to do a restore, or if you used replication, you just power up the replicated VM (Veeam uses de-dup technology so b/u and restore are faster than traditional b/u & restore technologies). Then, once the restored/replicated VM is backup, you connect your RDM to the restored VM (disconnect it from the crashed one 1st, of course).

That would cover you in the even of your server crashing; and your traditional b/u is used if you need to restore data.

Another idea to think about is EMC's Replistor. We use that at my org for images...2TB worth of data. You can't really backup images, yet we need b/u's of the data, so how does 1 achieve that?...replication to another server. So, we have a b/u file storage server VM that we have identical replicated (real-time) data on, so if our main file storage server VM (or its data) crashes, we have an instant replacement. My director takes care of that technology, so I can't provide the intricate details of its functionality, but it may be something to look into.

Hope something there helps...

What do you mean by 'wanting multiple VMs to be able to see the same disk space'?? Are you wanting to place a number of VMs on a single datastore, or are you wanting to create a volume (VMDK) file from a datastore and share it in your Guest so other VMs can 'see' it? If it's the latter of the two, then just create another Hard Disk in a VM and, assuming it's a Windows guest OS, share it out, then on the other VMs create a mapped drive (again, assuming their are all Windows VMs) to the share location.

LetterpartAuthor Commented:

thanks for your reply.

I am wanting to share our data between multiple VM's but not via mapped drives. If for example I create the HD on server 1 then share and map this to server 2, if server one falls over, the mapping on 2 fails and it can't see the data.
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OK...I understand now. Well, that's just the nature of file storage beit the physical or virtual realm. :)

What you can do is create a single file storage VM and then back it up using Veeam Backup & Replication. Well, let me stop there....before I continue, let me ask what your goals are. Because I can give a few answers here. :)

LetterpartAuthor Commented:
Lol, I was just sticking the kettle on there and sitting down comfortably....

What we have here is two webservers (webserv1 and webserv2) and two applications servers (appserv2 and appserv3). You can see I spent a lot of time thinking up the names here.

Webserv1 links to appserv1 and similarly for webserv2. Our customers upload word files via a browser and through Omnimark, Perl and some voodoo magic (rules based typesetting using XPP), we produce a print ready pdf out of the other end.

Our existing set up involves two virtual disks on the AX150, with each Appserver attached to its own disk and I snapshot VD1 and then Robocopy the data to VD2 during the day then destroy the snapshot ready to go again the next day so that in the event of Appserv1 falling over, Appserv2 has as near identical a copy of the data as possible.

We have tried other forms of replication but due to the nature of our data, we produce too many files too quickly. For example, each 3500 page book uploaded will create a file for each page. The XPP application we use keeps 3 revisions of the data at any one time so master becomes copy 1, copy 1 becomes copy 2 and copy 2 becomes copy3. This produces 3 x 3500 files and that is just one file upload. We have hundreds of files being uploaded and worked on internally all day long.

I was just hoping that I could get away from these snapshots and replicating between the two and have both Appserv2 and Appser3 looking at the same data.

Letterpart, to my knowledge you cannot share the same storage between file servers at the same time because it will cause corruption.  On the other hand, if you have a file server cluster, this will be allowed but typically will function as an active/passive cluster.  The way VMware gets around by sharing the same LUN across multiple hosts and VMs is because it uses a form of clustering to avoid corruption.
Allowing VMs to access Datastores is not possible. If you would like to have file store in side your ESX environment it is possible.  You can create a file server with Huge virtual disk(either windows or a openfiler virtual machine)
LetterpartAuthor Commented:
Thanks for your advice, I have also downloaded a copy of Veeam SCP and it is a very useful tool.

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