Virtualization 101: Disk provisioning options in vSphere

If you’re new to virtualization, there is a lot to learn. One of the more important items that you’ll need to understand is how to provision storage. In the figure below, you can see that the administrator is creating a new virtual machine with 20 GB of storage.

In the Disk Provisioning section, you will see three options. Here is a look at these three options along with how each operates.

  • Thick Provision Lazy Zeroed. When a disk is provisioned in this format, all of the specified disk space is allocated on the storage device, but the allocated space is not actively prepared ahead of time As the virtual machine expands to use the allocated capacity, the space will be cleared, resulting in what amounts to a negligible performance hit.
  • Thick Provision Eager Zeroed. As is the case with a Lazy Zeroed disk, the space required for a volume is preallocated on the storage device, but in this case, vSphere also zeros out any empty space on the volume. This disk type is required to support features such as Fault Tolerance. Disks provisioned in this format may take a long time to create.
  • Thin Provision. When you use thin provisioning, you’re telling vSphere that you want to ultimately allocate a certain amour of disk space to a vital machine but to only use enough disk capacity to support today’s needs and grow into the rest. For example, you may create a file server with 1 TB of disk space, but today, the VM will use only 60 GB since that’s how much data is stored in the VM. The danger in using thin provisioning is that you can accidentally oversubscribe your storage without realizing i/. As such, make sure that you carefully monitor storage to make sure you don’t run out.

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