Thick or Thin: Choosing the right provisioning method for your virtual machines

One of the many decisions that IT engineers must consider when creating a new virtual machine is how the storage on that machine should be allocated: thick or thin. Put another way, do you want the virtual machine to consume the amount of storage that it can potentially fill or would you like the new virtual machine to consume only the amount of storage that it is currently using?

There are good reasons for using either method. The two major types of provisioning have some advantages and drawbacks. When you’re making this decision, here are the things that you should consider.

Considerations for thick provisioning

Thick provisioning allocates all the space that could be used by the volume or virtual disk. This method consumes more storage space from the outset, but that comes with some distinct advantages.

  • You don’t have to worry about a large number of changes causing the hosting storage to silently fill up in the background.
  • This method provides you with a more useful, real-time view into what space is available on your SAN or host volumes.
  • In some rare circumstances writing data that causes thin provisioned drives to increase could be slower. Thick provisioned drives don’t face this issue.
  • On the downside, much more space is used on empty drives so your configuration should limit their size or you will need to have more storage available.

Considerations for thin provisioning

Thin provisioning only uses the amount of space on a volume that actually has data written to it. This method uses less space from the outset, but it could cause an issue in some circumstances.

  • The reduced storage requirement means that they can be configured and allocated much more quickly.
  • Since initially there is almost no space in use, you can create a large amount of virtual space in a fairly tight amount of physical space. This is especially useful for migrations or staging.
  • A large amount of changes causing a virtual drive to grow can fill the physical space, causing all drives sharing that space to suddenly fail because they cannot write data.

Summary and caveat

Overall, each method has its advantages and disadvantages. Thick provisioning, along with a proper design, does not require as much monitoring to avoid issues. While thin provisioning, along with careful monitoring and design, can save a lot of physical storage space while providing a flexible environment

If you have any further questions on how to best allocate your storage or if you would like a review of your storage environment and procedures, reach out to us at We would be happy to help.

By |2018-12-18T11:54:15-05:00September 18th, 2017|Infrastructure Services|Comments Off on Thick or Thin: Choosing the right provisioning method for your virtual machines

About the Author:

As the Storage Architect at Peters & Associates Dan is responsible for SAN and Backup design leadership as well as mentoring and troubleshooting guidance. He has many years of heterogeneous system integration with multiple hardware and software vendors. Dan has over three decades of experience working at Peters & Associates He has experience with SANs from multiple vendors on various infrastructures, primarily Fibre Channel and iSCSI. He has experience with multiple backup software products using various hardware platforms including DR, replication and cloud. Dan is also involved in providing optimal designs and sizing to support virtualizing mission critical applications on multiple virtualization platforms including VMware and Hyper-V.