Shared RDM or VMDK for NLB Cluster?

[motenoob12]

We have a 2012 R2 NLB cluster hosting a web application.  We would like to have a shared storage location that can be referenced by each server in real time.  I created a LUN and added it as both an RDM and VMDK, but the other server does not see the change unless I re-mount the drive.  I added the multi-writer string in the advanced options for both VMs thinking that may resolve the issue, but regardless - I suspect this could lead to an easy way of corrupting files.

With that said, what is the best approach to accommodating this?  We currently have a network share being referenced by each server, but to me that adds variables of a network issue causing problems, or the account used to authenticate against the share not working.

What other options do we have?

[rcporto]

Your setup will not work unless you install the Windows Failover Cluster in your Windows Server 2012 R2 to coordinate the access to the disk. But unless I'm missing something, Microsoft don't support install the NLB and WFC in the same machine. This way, the other option you have is create another two VMs, install WFC feature and create a File Share resource to be used by your NLB servers... and about the account authentication, just make sure you have more than one DC in your environment.

[NuggetGTR]

unless something has changed recently NLB and WFC can not be run together so that rules out that.

Unfortunately windows file systems by their very nature ever only allow one machine to own and read and write from the LUN. this is where CSV's (Cluster shared volumes) came in which is an abstraction layer but I don't believe can be used in your instance.

The multiple writer flag is only to allow multiple VMs to access the VMDK and physical RDM's dont require this, but this issue is a windows limitation.

The only really supportable way to do this from what ive seen is a network share which is what your doing, This can be a highly available share from a file server cluster, a NAS or making use of DFS.

[MKguy · Accepted solution]

We've been through this a million times recently.

NTFS (without CSV) is not a cluster-aware filesystem and as such can't handle simultaneous write access from multiple hosts to one block storage device. Your setup will not work in a purely physical world as well.

Please review these threads on the same topic:

Configure shared disks on 2 VMs hosted on 2 seperate ESXI hosts

Sharing virtual disk with two machichenes

[motenoob12]

All great, helpful replies.  Thank you MKguy especially.