5TB RDM on ESX 3.5 update 2

[JonBohlke]

Ok so before I looked at the vmware maximums document I created a 5TB LUN on my SAN an mapped it to a VM using physical mode. This in turn created a 1TB vmdk file and the VM worked fine. I have noticed that physcial mode RDMs always seem to be referenced by smaller sized vmdks but that was long ago. The fileserver is working fine, its a GPT disk of 5TB does this still fit in to the vmware maximums since the vmdk is only 1TB or am I going to run into trouble when this disk exceeds 2TB of used space?

[Texiwill]

Hello,

IN general it will run into problems. I would test this by formatting the RDM for the full 5TBs and see what happens. So you have a 1TB VMDK and a 5 TB RDM attached to the same VM?

Best regards,

Edward L. Haletky

VMware Communities User Moderator

====

Author of the book 'VMWare ESX Server in the Enterprise: Planning and Securing Virtualization Servers', Copyright 2008 Pearson Education.

SearchVMware Blog: http://itknowledgeexchange.techtarget.com/virtualization-pro/

Blue Gears Blogs - http://www.itworld.com/ and http://www.networkworld.com/community/haletky

As well as the Virtualization Wiki at http://www.astroarch.com/wiki/index.php/Virtualization

[JonBohlke]

The LUN is formatted and working fine, I have one RDM attached to this VM and it is 5TB. Currently the GPT formatted volume is only using about 100M.

[Texiwill]

Hello,

How did you create the RDM? Through the VIC, or are you talking about accessing an iSCSI LUn from within a VM? I think you will run into issues eventually. THere is a 2TB limit, but the size of the RDM should max be 1TB as that is the overflow.

Best regards,

Edward L. Haletky

VMware Communities User Moderator

====

Author of the book 'VMWare ESX Server in the Enterprise: Planning and Securing Virtualization Servers', Copyright 2008 Pearson Education.

SearchVMware Blog: http://itknowledgeexchange.techtarget.com/virtualization-pro/

Blue Gears Blogs - http://www.itworld.com/ and http://www.networkworld.com/community/haletky

As well as the Virtualization Wiki at http://www.astroarch.com/wiki/index.php/Virtualization

[JonBohlke]

I created the LUN on the Clariion and then presented it to the ESX servers. From there I added it to the virtual machine without error.

[JonBohlke]

Ok so I just got off of the phone with vmware and they say that a 5TB LUN will work in theory but they cannot guarantee the stability and performance of an RDM that large. 2TB is the max, time to reconfigure my fileserver

[philzy]

Hi!

No problems for 256 Tb RDM' for vm's that uses GPT-partitions (e.g. Windows server 2003 SP1).

Why? Read this - http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=100663...

The ESX storage stack limitation is residing in in its compliance with SCSI-2 standard. In the case of passthru RDMs, the

SCSI CDBs framed by the guest operating system (to do reads or writes)

are passed through by the PSA layer to the underlying storage.

This allows some guests to break the 2TB limit but this is

an unsupported configuration because the storage stack of the ESX is

not designed to handle such capacity.

[vmw-sfraser]

I'd still be very wary about this. All virtual SCSI controllers on ESX (except the LSI Logic SAS controller on ESX4) are 32 bit. You would still be at the mercy of the guest OS to address the LUN correctly with only a 32 bit controller.

This should work fine on a Windows 2008 (or equivalent OS that can handle addressing larger LUNs) and the LSI Logic SAS controller, as W2K8 uses SCSI-3 (64bit).

There are 10 types of people in this world. Those who understand binary, and those who do not.