How shared disks are supposed to work on VMware?

[vandreytrindade]

Hi,

I was reading this article on (How to Share Disk Between VMs on VMware ESXi – TheITBros) ITBros and decided to give it a try.

Here's what I did:

• Created two Windows 10 VMs (VMware tools installed)
• Added on each VM an additional a SCSI LSI SAS controller and configured them as Virtual
• On the first VM, created a disk allocated on the virtual device node SCSI 1:0, thick provision eager zeroed type and set it to Independent - Persistent
• On the second VM, added that existing disk and set it to Independent - Persistent
• Since my vCenter is version 5.5 I had to add the multi-writer configuration manually (VM Options > Advanced configuration > Edit Configuration > Add row > scsi1:0.sharing = "multi-writer"
• Powered-on first VM and formatted the disk
• Powered-on second VM

So I created a folder on the first VM and it didn't appeared on the second VM. I needed to restart the second VM so it updated the hard disk information.

It isn't supposed to refresh automatically?

[wila]

Hi,

Windows 10 is not an OS that is capable of working with clustered disks.

See also:

How to Configure a Clustered Storage Space in Windows Server 2012 | Clustering and High-Availability

You'll need a server OS and that has to be set up for clustered storage for the shared disks.

Normally an operating system expects (nee demands) to be the only master of who writes to the disk.

If you have two operating systems writing to the same disk then -unless it has been designed to allow clustering- data corruption will occur.

When both systems are writing to the file allocation tables and assigning clusters "Bad Things Will Happen" (tm)

The standard way to share storage between multiple systems is to use network sharing. That way you ask the other system to write data to the disk on your behalf.

--

Wil

[vandreytrindade]

wila,

Thanks for replying.

I deleted the old lab and recreated it using Windows Server 2012 R2 for the two VMs.

Still the same thing: create a folder on the first VM, it doesn't appear on the second VM until a restart.

Checked that website that you have sent to me and when I try to create a new storage pool it didn't show any disks.

I was reading some sites about the shared disk and noticed a configuraion disk.locking = "FALSE". Maybe it has something to do?

[wila]

Hi,

I don't know as I have no need for a Microsoft cluster.

But I do know the basics and that you'll have to setup a quorum disk and that it is a bit more as just assigning the same disk to two virtual machines.

An example configuration is discussed here:

http://wojcieh.net/microsoft-cluster-running-on-vmware-esxi-cluster-in-a-box/

Hopefully that gets you started.

--

Wil

[vandreytrindade]

wila,

Thanks again.

But that's my questions:

• The only way to get benefit from using a shared disk is using it on a cluster?
• That is the only way to get it working the way I want?

[wila]

Hi,

Yes, that's correct.

Having direct disk access from 2 (or more) operating systems is a very special use case and not a common scenario for sharing files between two systems.

This is typically used in high availability (HA) scenarios, but those are normally on two different physical systems, having a HA system located on a single host defies its primary goal.

Normally this is setup to guarantee your server continues running even when there's a hardware failure (removing the single point of failure).

--

Wil

[vandreytrindade]

Thanks for your time and attention!

[itcwiproserver]

shared disk will work only if they windows server are in cluster.

If windows server is not in cluster , disk should be online in one server and offline in other server.