ESXi 6.5 and RDM - incompatible backing for device ....

[kweiland]

Ha all,

since more than 2 weeks i'am trying to add a RDM disc to an already existent or to a new VM. I have already read tons of docu's/posts but i am unable to find a solution.

Maybe one of you can give me a hint 😉

Tried with ESXI 5.x, 5.5, 6.x and 6.5 .....maybe there any logfile stored where i can find more details ?

bought : HP ProLiant gen8, G1610T, 4GB, HP B120i

added parts : 1 x 8GB RAM, 2 x 256GB SSD RAID1, 2 x 2TB HDD RAID1, ESXI 6.5 free HP custom iso successfully installed and configured on MicroSD

Cheers

[TheBobkin]

Hello kweiland,

Can you give a bit more information please? Is this a pRDM or virtual RDM?

You are having issues with adding it to a second VM or issues with creating/adding it to first VM? (I am assuming you are setting this up for guest-OS level clustering/shared-disks).

Look in the vmware.log of the VM you are attempting to add this to and/or attach them to comment so that we can take a look.

Are you seeing anything similar to the output noted here?:

https://kb.vmware.com/kb/2054897

Bob

-o- If you found this comment useful or answer please select as 'Answer' and/or click the 'Helpful' button ,please ask follow-up questions if you have any -o-

[kweiland]

Hi Bob,

thanks for replying 🙂

My current configuration : 2 x 256 GB SSD RAID1 on HP B120i, 2 x 2000 TG HDD on HP B120i. ESXi datastore configured as follows : 256GBSSD, 2000GBHDD - VMS6. Successfully created RDM's disc's on both datasores follwing the directives from https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=10175... (not sure, it this is a pRDM or vRDM).
Currenly 2 VM's (Win10, WIn2012R2 both are freshly created with ESXi) are stored on datastore 256GBSSD. Trying to add the RDM disk located at datasore 2000GBHDD to one/both of theses VM's, running into error 'incompatible backing for device 3'.
I am trying this since more than 2 weeks without success - tried with ESXi 5.0, 5.5, 6.0 and current 6.5 - always the same error..

Will check/attach the VMware.log later.

Cheers

[a_p_]

You mentioned "2 x 256GB SSD RAID1, 2 x 2TB HDD RAID1", so on which disk/volume are you trying to create the RDM? A RDM is a mapping to a previously unused disk/volume, i.e. one that's not already in use as e.g. a VMFS datastore.

What's does ls /vmfs/volumes/disks show? And which exact command did you use to create the RDM?

André

[kweiland]

Hi Andre,

maybe thats my fault 😉 - not known, that the RDM file can't be stored on a already configured ESXi datastore....

Followed the directives from https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=10175...​ to create the RDM disk.

Will try to delete the datastore (2000GBHDD) and setup a new RDM disk again.

Cheers

[kweiland]

ls -l /vmfs/devices/disks is showing

-rw-------    1 root     root     256022937600 Mar 19 17:30 naa.600508b1001c3f9b27a5d7d8194f0d8a (datastore configured in ESXi - 2 x 256 GB RAID1)

-rw-------    1 root     root     256022852096 Mar 19 17:30 naa.600508b1001c3f9b27a5d7d8194f0d8a:1

-rw-------    1 root     root     2000365379584 Mar 19 17:30 naa.600508b1001cc8c8885010444c2b0344 (datastore not configured in ESXi - 2 x 2000 GB RAID1)

does not work without configured datastore in ESXi because valid datastorename must be available ...

-> vmkfstools -z /vmfs/devices/disks/diskname /vmfs/volumes/datastorename/vmfolder/vmname.vmdk

cheers

[a_p_]

The command will create a mapping file (actually two .vmdk files) on the datastore you specify. If you want to use the RDM with an existing VM, consider to create the mapping file in the VM's folder (i.e. on the existing datastore that you've created on the SSD RAID).

André

[kweiland]

Reset and reconfigured array

Fresh reinstallation ESXi 6.5 done

2 new datastores created (256GB-RAID1 & 2000GB-RAID1 - both are VMFS6)

1 new VM installed (WIN10VM1 on 256GB-RAID1)

ls -l /vmfs/devices/disks is showing

-rw-------    1 root     root     256022937600 Mar 19 20:14 naa.600508b1001c3f9b27a5d7d8194f0d8a

-rw-------    1 root     root     256022852096 Mar 19 20:14 naa.600508b1001c3f9b27a5d7d8194f0d8a:1

-rw-------    1 root     root     2000365379584 Mar 19 20:14 naa.600508b1001cc8c8885010444c2b0344

-rw-------    1 root     root     2000365294080 Mar 19 20:14 naa.600508b1001cc8c8885010444c2b0344:1

vmkfstools -z /vmfs/devices/disks/naa.600508b1001c3f9b27a5d7d8194f0d8a /vmfs/volumes/256GB-RAID1/WIN10VM1/RDM.vmdk

TRying to add the RDM as follows

same problem still exist

Cheers

[a_p_ · Accepted solution]

... same problem still exist ...

That's because you are still trying to create a RDM on a disk which is used as a VMFS datastore!

Assuming that you want to use the 2TB disk/volume as a RDM (Raw Device Mapping), you must not have any partitions on that disk/volume, and create the RDM with the resulting .vmdk files (which then point to the 2TB disk/volume) on a VMFS datastore.

So after deleting the currently existing VMFS partition on the 2TB disk/volume, run

vmkfstools -z /vmfs/devices/disks/naa.600508b1001cc8c8885010444c2b0344 /vmfs/volumes/256GB-RAID1/WIN10VM1/RDM.vmdk

to create a 2TB RDM.

André

[kweiland]

Yeah, thats it !

Thank you very, very much André to pointing me into the right direction.

Sorry for my misunderstandig about how to sucessfully create a RDM.

Cheers