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Delays When Writing to a New Virtual Disk for the First Time (2191)


Writing to a new virtual disk takes a long time. Is this normal?


Yes, this is normal behavior. You may experience delays on the first write to a newly created virtual disk. Subsequent writes are not affected. Also, there are no delays when you move a clean virtual machine from another VMFS-3 or VMFS-2.5.

To avoid delays on the first write, do one of the following:

  • Use vmkfstools -c -d writezeros to create a new virtual disk and zero it out in one step.
  • Use vmkfstools -w to initialize the content of the newly created virtual disk to zeros.
  • Use vmkfstools -j to inflate a thin virtual disk to preallocated and zeroed out. No existing data is modified. Make sure you do the md5sum of the -flat.vmdk before and after the operation to verify that the disks are identical. The inflate option works only on VMFS files. It doesn't work on virtual machines that are already preallocated.
  • Deploy a template.
  • Clone an existing virtual machine.

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