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gtlscot
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Contributor

Automation/Management of RDM Disks

Hi

In our environment we have 5 virtual clustered MS Exchange servers configured for our exchange DR plan. These servers were built by our system integrators. However the key design and configuration of these has not been clearly documented and the individual responsible has since departed to Oz. The set-up is as follows:

5 VMs each with a fixed OS partition and shared storage for the quorum. Each of the machines are also configured with 18 RDM disks that point to areas on the SAN that become visible once our secondary site is presented. The naming of the RDM files is as follows:

Disk1 through to Disk18 located within a folder named DRCluster on the LUN of the virtual machine resides e.g. virtual machine name server1 is in folder on LUN called server1. All RDM files are in the folder DRCluster.

Recently there was as requirement to increase the capacity of the production Exchange LUNs from 500GB to 630GB. The knock on affect of this change is that one of the RDM LUNs previously created was the incorrect size. This stopped the VMs starting with the following error: "Cannot open the disk

'/vmfs/volumes/490b4e6a-a8a6bb95-bb45-001e4f277ad5/ExDRcluster/disk18.vmdk' or one of the snapshot disks it depends on. Reason: No such device"

To correct this problem all that was required was to remove the offending RDM mapping and re-create. The machines now power on. However, this is where our issues have started. When we create a new RDM from within server1 we have struggled to re-name this RDM to disk 17 as the default name that it takes is virtual machine guest name. Strangely though the RDM file is shown in the DRCluster folder on the SAN rather than the server1 folder in the same location.

We are looking for guidance using the command line vmkfstools command or similar on how we change the name of this RDM to disk17rather the default name of server1_1.vmdk. We know to enable these disks with the re-maining machines within the DR cluster that we just need to copy the entry within the VMX file and re-register.

Hope this all makes sense

Thanks

Graeme

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