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Copying Virtual Disks from one VMFS Partition to another

Copy a virtual disk from one VMFS partition to another VMFS partition

Suppose you want to copy a virtual disk in the monolithic format on one VMFS partition to another VMFS partition?...

Before you reach for the cp command at the Service Console – beware! When you use copy command in this way – every couple of MG the VMkernel has to put a non-persistent SCSI reservation to update the VMFS File System (commonly referred to as “metadata”) This constant imposition of SCSI Reservation can undermine performance on access to the VMFS partition – and could potentially cause an error.

So what is the alternative? Well, a straight “copy & paste” from the MUI File Manager is safe – and so is vmkfstools. They place a non-persistent reservation on the VMFS volume, and quickly release it once the monolithic file has been created. These tools then use “file locks” to then copy the data to the VMFS volume in question – which doesn’t impose volume wide SCSI reservations. 

Remember don’t trust non-VMware file management tools to handle the SCSI reservation issue correctly – as they not VMFS and VMKernel aware 

Normally if you using the -I switch in vmkfstools its to import a virtual disk in the COW (template) format to a VMFS partition. But it can also be used between vmfs partitions  

If you are using vmkfstools this is the syntax you would use: 

vmkfstools -i /vmfs/local/server1.vmdk /vmfs/san-lun10/server1.vmdk

Remember to update the Virtual Machine configuration (VMX) to point to the new location

This was last published in December 2005

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