4TB RDM Volume with Raid Controller

[jgkurz]

Hi Everyone,

I have read thread after thread on RDM and I now need to make a inquiry to the group. I have an ESXi 5.0 host with a 3ware 9650SE raid controller. After updating the driver ESXi now sees the 3ware controller just fine. I can format in VMFS and create 2TB vmdk volumes just fine. At this point there is no data on the array so I would like to experiment with RDM. My desire is to mount a 4TB RDM volume to a guest. I do not need snapshot or other VMFS features for this storage. As we all know, VMFS is now capable of larger than 2TB but VMDK's are still limited to 2TB.

If I go to my guest and create a disk the Raw Device Mode is always greyed out. All the RDM instructions on this forum indicate that a 4TB LUN is possible but from a SAN.

Is a 4TB RDM volume possible on an internal hardware raid controller?

Thank you!

-John

[Dave_Mishchenko]

It's possible, but not supported.  If this is a production machine you have to consider that statement very carefully.  http://www.vm-help.com/esx40i/SATA_RDMs.php

[jgkurz]

Thanks for the response!!  It's not production and in this case I am OK with the workaround being unsupported.

I have previously read the article you posted. Is it correct to assume that because the newly created VMDK is a just a pointer to my RDM volume that it will not limit me the the 2TB?

[Dave_Mishchenko]

That's right.

[jgkurz]

Thanks Dave. I'll follow the instructions and see if I can get the RDM volume mounted.

[jgkurz]

I followed the instuctions and I keep getting the message "Unable to create virtual disk with specified parameters" when I enter the follow command in VMware CLI.

mkfstools.pl --server ???????? --username root --password ?????? -r /vmfs/devices/disks/vml.0100000000395653343158564b314532443131303041393033393635305345 /vmfs/volumes/3ware9650se-rdm.vmdk -a lsilogic

Any suggestions?

[Dave_Mishchenko]

The RDM pointer file has to site on a VMFS partition so this

/vmfs/volumes/3ware9650se-rdm.vmdk

should be something like

/vmfs/volumes/<datastore_name>/3ware9650se-rdm.vmdk

[jgkurz]

Nice catch!  I missed that.

With the path corrected I still get the "Unable to create virtual disk with specified parameters" message but now VMware vSphere Clients reports "A specified parameter was not correct.  spec.device"

This is what I'm entering.

vmkfstools.pl --server ???.???.???.??? --username root --password ?????? -r /vmfs/devices/disks/vml.0100000000395653343158564b314532443131303041393033393635305345 /vmfs/volumes/1TB-SATA/3ware9650se-rdm.vmdk -a lsilogic

[jgkurz]

I have triple checked my vml identifier and it's correct, still no luck.  Thanks for you help.

[jgkurz]

Here's the error from my /var/log/hostd.log after I run the vmkfstools.pl -r.

[kjb007]

You need to use a physical mode RDM for greater than 2 TB, so you should be using vmkfstools.pl -z

-KjB

[jgkurz]

That did it!!!!!   Thanks to both of you for getting me pointed in the right direction. Much appreciated.

[leejb]

Quick question. The article you refer to is labled as ESXi 4.0.  The specs on ESXi/vSphere 5 http://www.vmware.com/pdf/vsphere5/r50/vsphere-50-configuration-maximums.pdf do show 64TB phsyical with no annotation to any support limitations.  Granted its now 5Update1 and 5 months later, but I'm considering virtualizing two servers bind a 4TB volume each which I'm thinking I can do w/o making any changes other than the P2V and RDM setup.  If its truely not supported...

Anyway, thought I would ask.

[kjb007]

That statement was for a local SATA/SCSI based RDM, and not a SAN based RDM.  SAN based RDM's on VMFS5 are supported.

-KjB