RDM Disk mapping file move to different Data store

[JoBob]

Hello Team..

We have a Windows Cluster environment on VMWare with essentials plus license,for which we are using physical RDM Disks

so these physical RDM Disk mapping files are placed on a datastore DATASTORE-A which is accessible to all the hosts (SERVER-A and SERVER-B)

example for  SERVER-A-VM and SERVER-B-VM there is a shared physical RDM disk by the name DATA kept on a datastore DATASTORE-A, it is working.

Now the question if we have another datasore DATASTORE-B which is also accessible to all the hosts, and we move the RDM mapping files from DATASTORE-A to DATASTORE-B, and then attach the RDM Disk files from DATASTORE-B,by using the option -Use an existing HDD in VMWare , will it work?

Because when we tested this ,it did allowed to add the Disk in the server,but the same LUN will be shown as available for a new RDM ,if we try to add a new RDM disk.( physical LUN path will not be shown it was adding as a normal vmdk)

Thank you..

[TheBobkin]

@JoBob Your question doesn't seem to have anything to do with VMware vSAN, you have posted this in the vSAN sub-community. I would advise you or a moderator move this to the relevant sub-community (e.g. ESXi/Storage).

[JoBob]

hello I do not see an option to move..

[pashnal]

Hi Bob, 

Yes you can move the mapping files and attach them as an existing HDD . If its a production cluster this is how I would do . 

1. During the downtime window for  Cluster VMs, Remove the  HDD (VMDKs) from secondary Cluster VM . 

2. Migrate (Storage vMotion ) the VMDKs (Mapping files) to other datastore and then Connect them to secondary VM  as existing HDD 

Please mark my comment as the Correct Answer/Kudos if this solution resolved your problem Thank you.

Thanks , 

Pramod Ashnal 

[JoBob]

@pashnal Thank you for the reply..

ok so Storage vMotion is the option?

but if we do not have the license for it , can we move using gui or console ?

we tried using GUI and it looks like it broke the chain to RDM and when we attached as an existing HDD ,it did not show the Physical LUN path under the HDD, instead it was like a normal vmdk file, and the LUN that was used for RDM was shown as free and available

[pashnal]

If you have  license issues for Storage vMotion , Then remove the RDM from both the VMs(Do not delete the files ) and then add the RDMs by selecting the new Datastore(for mapping files) to primary VM  and then add the HDD as existing HDD to other cluster secondary VM . 

Thanks , Pramod Ashnal 

Please mark my comment as the Correct Answer/Kudos if this solution resolved your problem Thank you.

[JoBob]

@pashnal  you did mention-Then remove the RDM from both the VMs(Do not delete the files )  ie did you mean remove the attached RDM Disk from the VM ,without deleting the RDM mapping files(xxx.vmdk and xxx-rdmp.vmdk ) from datastore (without checking that box to delete)?

so after adding the RDM on to the VM by using the new Datastore it will gain create the mapping files (xxx.vmdk and xxx-rdmp.vmdk ) on the new datastore right?

So the old RDM mapping files  (xxx.vmdk and xxx-rdmp.vmdk ) will still remain on the other Datastore ,unused?

Instead will it allow to move or copy the mapping files  (xxx.vmdk and xxx-rdmp.vmdk ) to another Datastore and then map this to the Vm as an existing HDD without breaking the mapping files link to the LUN?

[pashnal]

1. Yes , Do not check the box which says delete the file while removing the RDMs (Caution)

2. Yes ,when you remove the RDM from VMs it will also remove the mapping files automatically there will not be any residual files .

Order of removing

a.) Removed the mapped vmdks from secondary VM

b.) remove the RDMs from primary VM . 

3. When you add the RDM again by selecting the new Datastore then it will create a new mapping files . (This is the best method if you do not have Storage vMotion) and I recommend you to do this . 

4. You cannot copy the mapping files to another datastore and make it work as the system and VM (Primary) dose not know that you have moved the mapping file . 

Thanks , 

Pramod Ashnal 

Please mark my comment as the Correct Answer/Kudos if this solution resolved your problem Thank you.

[JoBob]

@pashnal 

1. Yes , Do not check the box which says delete the file while removing the RDMs (Caution)- why ,RDM the actual data resides on the storage directly right? so only the mapping files will only gets deleted ?

but When i removed the RDM disk without checking the delete box, the files (xxx.vmdk and xxx-rdmp.vmdk) still resides, but if i check the delete box then these files got removed. 

4. You cannot copy the mapping files to another datastore and make it work as the system and VM (Primary) dose not know that you have moved the mapping file . - am moving the mapping files (xxx.vmdk and xxx-rdmp.vmdk)  manually to a new datastore,and then linking the file to the VM as adding an existing HDD,

The files xxx.vmdk and xxx-rdmp.vmdk are these the mapping files or is it something different wrt to RDM ?

[pashnal]

Hi @JoBob 

1. why ,RDM the actual data resides on the storage directly right? so only the mapping files will only gets deleted ?

Yes 

but When i removed the RDM disk without checking the delete box, the files (xxx.vmdk and xxx-rdmp.vmdk) still resides, but if i check the delete box then these files got removed. 

Not Sure but RDM will loose association with the mapping files 

4. You cannot copy the mapping files to another datastore and make it work as the system and VM (Primary) dose not know that you have moved the mapping file . - am moving the mapping files (xxx.vmdk and xxx-rdmp.vmdk)  manually to a new datastore,and then linking the file to the VM as adding an existing HDD,

The files xxx.vmdk and xxx-rdmp.vmdk are these the mapping files or is it something different wrt to RDM ?

As mentioned earlier , When you manually move the mapping files VM will not be aware that you have moved the files and it will break the association . 

Please mark my comment as the Correct Answer/Kudos if this solution resolved your problem Thank you.

Thanks , 

Pramod Ashnal