clarifcation about exporting and Importing a virtual machine and Raw Device Mapping between the virtual machines

mu3tasem
mu3tasem used Ask the Experts™
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Hi Experts ,

I did export and import for a virtual a mchine from one host to another and it worked fine and the restored machine working propely ..

my Questions :

1- i faced IP address issue with the new one so re assigned the IP manually through the OS .. is there anothery way to solve this issue from the begining or this is how it should go?
2- I want to do another Export for this restored system after some modfication on application level  but  iwant to imorte it to the same host .. will that make any problemfor me? i am just renaming the virtual machine name from inventory so the internal folders as it is.. howerver if no issue to keep both systems on same host i want to keep it simple process
3-my Application vendor is asking for shared (RDM) LUN between the 2 virtual machines for os cluster purpose  ,, can you advise step by step how to do the RDM?
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Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
1. There should have been no IP issues, but it depends on how you Export and Imported, and if there was any display prompts your responded to.

2. There should be no, issues other than changing the inventory name, and making sure the MAC Addresses and IP Addresses are unique.

3. Do you have shared storage you can use, to create the RDM from your iSCSI or FC SAN ?
nociSoftware Engineer
Distinguished Expert 2018

Commented:
1) IP issues do  exist when there is a static assigned address. If DHCP is used there should be no problem.

2) You need to be away that all external items (MAC Addresses, WWID's, (Upper layer addresses like IP, .. ) or in general: Network Addresses are causes for confusion by the uotside world.  So they need to be renewed/replace on or after import.

3)  IS THERE ANY WAY of synchronizing access to this shared LUN by the OS'es?....
(Compare OpenVMS Distributed Lockmanager, Linux GFS DLM)... if there is none, the disk will be destroyed in short time (seconds after mounting a disk) by both systems accessing it at the same time.

Author

Commented:
Hi Andrwe ,
1)      The export and Import  has been done through ( vsphere client ) , by exporting OVA template and deploy it. I didn’t get any wizard to respond to it ..the restore completed successfully but in both cases restore to different host or same host I need to manually reconfigure the IP address
2)      The restore worked fine but as I said network side needs to be reconfigure
3)      Yes I have  a SAN (FC protocol ) both hosts can see the same data store is this wrong design ? as I did this for vmware HA purpose  and vmotion .. and if it is a healthy design please provide me the steps  and best practice for RDM .. as I said the goal to implement cluster on Operating system level and this is a REQUIRMENT received by the vendor
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Author

Commented:
Hi Noci ,
1)      Yes it is Static , so you mean I need to repeat the network reconfiguration whenever the static ip exists ?
2)      I reassign the same IP to the machine as so many users  linked with it .. any concern about this ?cause it is really hard to change the IP to new one
3)      I am not sure about this , THE VENDOR asked me to prepare the RDM in vmware but I don’t know about the sync on the os level .. so Please adivse if I have to request them for any of the sync method for OS as this server will be for production and have valuable data.. the OS will be redhat Linux  7.4

Author

Commented:
experts ,

Can you please assist how to create a share RDM LUN between 2 VM servers (step by step) considering available SAN stroage

thank you
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
You can ONLY share an RDM by using Microsoft Failover Clustering.

Author

Commented:
we will install Linux redhat for those VMs so what is the scinario in such case ?

it should not be done through VMware itself ? i see the option to add RDM  for new devcies is so what is that for ?

i am really confused
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
Okay, you cannot actually share a RDM between VMs.

You will need to ensure that you have software on the VMs, which can handle clustering.

What do you want to implement ? What is your requirement ?

Author

Commented:
Hi I am sorry if i am not clear i will rexplain

I want to implement Linux Redhat Cluster between 2 new Virtual Mchaines

the linux installtion it self and cluster will be managed by a vendor , he send along with the requirment

** QOUTE : I need Shared RDM LUN between VM1 and VM2 with 500 GB**

the vendor said that this should be done from VMware side  ,  what I did : from SAN is to create a LUN with 500 GB and shared betweeh the 2 Esxi hosts where vm1 and vm2 resides(vm1 on exis1 and vm2 on exsi2)  but  i didnt initate it as datasotre as per my understanding to keep it for RDM creation . now if  i go to add RDM wizard i can the see the 500 GB created but my concen how i am going to share it in such case as you can add exising harddisk only not exising RDM disks.

so Please let me know if there is somthing worning in my understanding or the way for implementing is not proper and there is anotehr suggested way
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
Linux Redhat Cluster between 2 new Virtual Mchaines

Okay..... so to Cluster between 2 VMs (Red Hat), you can either use RDMs or Virtual Machine disks (VMDKs).

Do you have a SAN ?

Author

Commented:
Yes I HAVE SAN ,  the requirment is to use RDMS as per vendor

so how to apply this to my scinario ?
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
Okay, so you create a LUN on your SAN, present it to the ESXi Host, and then follow this link

https://www.vmadmin.co.uk/resources/35-esxserver/58-rdmvm

That RDM needs to be then added to both VMs, and then install your Linux OS and Cluster Software.

Author

Commented:
I am using version 6.7 and that link for older version of
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
It's exactly the same, it's no different, other than you now have a GUI.

But basically add storage, and select RDM, here is a Link for vSphere 6.7

https://docs.vmware.com/en/VMware-vSphere/6.7/com.vmware.vsphere.vm_admin.doc/GUID-4236E44E-E11F-4EDD-8CC0-12BA664BB811.html

Author

Commented:
HI Andrwe ,

can you please check the below and the layout uploaded  ... it is excatly my scinario

https://docs.vmware.com/en/VMware-vSphere/6.7/com.vmware.vsphere.storage.doc/GUID-BF12CB06-EB12-4536-BD9F-BBDC87F88691.html?hWord=N4IghgNiBcIEpgO4AIAiBTAbgSwMbuQFkwAHE7AOwHMQBfIA

I can create the RDM for VM3 like the layout  .. what i am missing how i will make vm4 see the same RDM LUN ..
GUID-1EA23ED6-1BF0-4E12-BDA5-2CA6BCB.png
VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017
Commented:
So you've created the above, now you need to install the OS, for Linux Clustering.

Please note that only a single VM will have access to the LUN at one time, both cannot write to the LUN concurrently.

So the LUN swaps from VM3 to VM4, with the OS software.

This is how you setup the VMs

https://blogs.vmware.com/apps/2015/02/say-hello-vmotion-compatible-shared-disks-windows-clustering-vsphere.html

(ignore it's for Windows Clustering, it's the same, other than the OS in the VMs)

Author

Commented:
Hi ,

I finally FOund the Missing Part for this Task :)

we got to know how to add  the RDM to and below the steps in order to share it with another VM

1- go to the second VM
2- Click add exisitng hard disk
3-slelect same Scsi COntroller
4-when it is asking for the disk location browse the datastore which has the mapping
5-Click add
6- click  ok

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