billtenbroeck
Contributor
Contributor

Shared Storage

Hello. I am brand new to VMWare, and I'm trying to setup an ESXi Server to replace 3 standalone servers. My last task before beginning to convert my physical machines over is to setup some sort of shared storage between to virtual machines. I had assumed that a virtual disk would be able to be shared, but according to KB 1012706 "You cannot share the same VMDK between multiple guest operating systems because it would lead to disk corruption." To say I was suprised would be an understatement.

I guess my question is: how do the folks who have been using this for a while deal with this? I'm sure mine is not an isolated need. I'm looking for suggestions and possibly pointers to help figure the best way to approach this. Any idea is welcome.

Thanks kindly.

Bill

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7 Replies
wila
Leadership
Leadership

Hi,

Welcome to the VMware community forums.

>My last task before beginning to convert my physical machines over is to setup some sort of shared storage between to virtual machines. I had assumed that a virtual disk would be able to be shared, but according to KB 1012706 "You cannot share the same VMDK between multiple guest operating systems because it would lead to disk corruption." To say I was suprised would be an understatement.

That's normal and mostly a limitation of a normal guest operating system. You can for example setup Microsoft clustering with a quorum disk, but I don't think that it is what you are asking.

It is the same in the physical world, a plain operating system expects to be the one and only master of the file system and the way we solve this in both physical and the virtual world is by file sharing over a network. Smiley Happy

Now having said that.. if you move up a level to your ESXi host, then you CAN share the same storage between different hosts. So you can have multiple ESX/ESXi hosts connect to the same LUN on shared network storage. That way it is easy for a host to fail over or to have a guest start up on another host. But that wasn't your question.

Hope this helps,



--

Wil

_____________________________________________________

VI-Toolkit & scripts wiki at http://www.vi-toolkit.com

| Author of Vimalin. The virtual machine Backup app for VMware Fusion, VMware Workstation and Player |
| More info at vimalin.com | Twitter @wilva
weinstein5
Immortal
Immortal

The question I would ask how do you currently share data between your three standalone physical servers? You just need to replicate that within the three virtual machines -

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weinstein5
Immortal
Immortal

deleted duplicate entry -

Message was edited by: weinstein5

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billtenbroeck
Contributor
Contributor

Gents, thanks for your replies. When looked at from that perpective, it kind of changes things. Smiley Happy

Looks like I'll be setting up a file server...

Thanks again,

Bill

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jeffmeden
Contributor
Contributor

I don't want to thread jack but the comment about using the same LUN across multiple physical hosts to allow easy migration... Is this something that is implied as being supported entirely by the iSCSI standard, or are there hardware and software guidelines that need to be followed? The reason I ask is I tried to run a single LUN between two hosts and while it worked great at first, over time I noticed file corruption, files frozen in place and other strange things. The only conclusion I came to was that it wasn't practical given my hardware and software, since I could find no 'smoking gun' issue that caused the corruption.

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wila
Leadership
Leadership

Yes, it should work OK.

What are you using for an iSCSI implementation?

I know that in older iscsi linux implementations there was issues similar to what you describe.



--

Wil

_____________________________________________________

VI-Toolkit & scripts wiki at http://www.vi-toolkit.com

| Author of Vimalin. The virtual machine Backup app for VMware Fusion, VMware Workstation and Player |
| More info at vimalin.com | Twitter @wilva
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jeffmeden
Contributor
Contributor

This is using the software iSCSI client in ESXi 4 rev 208-something, connecting to an iSCSI SAN device which is a dell MD3000i. I cannot guarantee that it was something related to contention between the two hosts but I don't know what else to look at, the VFS information and diagnostic measures are severely lacking (unless i am missing something.) Thanks for the advice!

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