Thin Provision vs Thick Provision: How to Choose the Right One?

What is storage provisioning

When creating and using virtual machines, you may have heard of thin provisioning and thick provisioning. They are 2 different kinds of storage provisioning strategies.

Storage provisioning is the process of assigning storage to optimize the performance of a storage area network (SAN), usually in the form of server disk drive space.

Thin provision vs thick provision, which is better? And how to choose from them? In this article, I will introduce the pros and cons of thin and thick provisioning respectively.

What is thin provisioning

Thin provisioning is a storage pre-allocation strategy that takes up only as much space as it initially need at creation, and grows over time based on demand.

The divisions on physical storage are virtual and flexible, rather than predetermined. As users save more data, they take up more space of the disk.

✦ Pros

High Storage Utilization: Thin-provisioned virtual disks take up less space at creation, and unused disk space can be used for other needs, which saving enterprises upfront storage costs.

Quick Creation: Faster creation for thin-provisioned virtual disks since they are small initially.

✦ Cons

Over provisioning: Provision more storage space than is actually available may lead to over-provisioning, which needs to be prevented by careful monitoring.

Manual shrink after data deletion: The disk size will not automatically reduce when you delete data from a thin-provisioned virtual disk. You need to shrink it manually.

What is thick provisioning

Thick provisioning is a provision strategy that takes up all storage space allocated from the beginning. Even if no data is written to disk, the unused physical storage cannot be used for anything else.

There are 2 types of thick-provisioned virtual disks.

• Lazy zeroed thick disk is a disk whose size is set at creation, but does not immediately erase or overwrite the old data on the blocks. Instead, these data will be zeroed out later when new data is written to the blocks for the first time.
• Eager zeroed thick disk is a disk that erases the old data on the blocks as soon as it is created. It takes longer to create but will be faster on the first write.

✦ Pros

Space predictability: The disk size is set at creation time, thus no over-provisioning.

Less Latency: Provides less latency since all storage space is pre-allocated.

Less Monitoring: Thick provisioning require larger LUNs, which means you don't have to re-do them when storage capacity needs a boost.

✦ Cons

Space Wasted: The unused storage space cannot be used for other things.

Longer Creation Time: It takes longer to create a thick disk for it is larger than thin disks initially.

What is the difference between thin and thick provisioning

After my introduction above, I believe you already have a general understanding of thin and thick provisioning. In this section, I will make a more visual comparison of them so that you can choose the suitable type of virtual disk to create.

Thin Provision vs Thick Provision

Provision type	Thin provisioning	Thick provisioning
Total disk size	grow as data written	fixed
Size at creation	smaller	larger
Space saving	yes	no
Creation time	shorter	longer
Latency	more	less
Need Monitoring	more	less

Thin provision vs thick provision: How to choose from them

As you can see, both thin provisioning and thick provisioning has their advantages and disadvantages, you may need to choose according to your situation. You can consider from the following factors.

• If you don't need to worry about saving storage space, and need better disk performance and security, thick provisioned disk is the more suitable choice for you.
• If you have a limited budget, want to save storage space, and are not very demanding on latency, creating a thin-provisioned virtual disk may be better.

Summary

When creating a virtual disk you have 2 storage provisioning types can choose from, thin provisioning and thick provisioning. In this article I introduced what is thin provisioning, thick provisioning, and what are the differences between them. I hope this could help you make a more suitable choice.

After creating a virtual machine, you still need to create backups to protect the data on these virtual disks. It's recommended to use professional and free VM backup software as there's no real backup option comes with VMware or Hyper-V.