Thick and Thin Provisioning for VMware Disks: What is the Difference?
In this article, we are going to consider the storage pre-allocation aspect of virtual disk settings in detail and find out what thick and thin provisioning are, how they differ, and which of these storage pre-allocation types is better for your infrastructure.
Thick provisioning is a type of storage pre-allocation. With thick provisioning, the complete amount of virtual disk storage capacity is pre-allocated on the physical storage when the virtual disk is created. A thick-provisioned virtual disk consumes all the space allocated to it in the datastore right from the start, so the space is unavailable for use by other virtual machines.
There are two sub-types of thick-provisioned virtual disks:
- A Lazy zeroed disk is a disk that takes all of its space at the time of its creation, but this space may contain some old data on the physical media. This old data is not erased or written over, so it needs to be “zeroed out” before new data can be written to the blocks. This type of disk can be created more quickly, but its performance will be lower for the first writes due to the increased IOPS (input/output operations per second) for new blocks;
- An Eager zeroed disk is a disk that gets all of the required space still at the time of its creation, and the space is wiped clean of any previous data on the physical media. Creating eager zeroed disks takes longer, because zeroes are written to the entire disk, but their performance is faster during the first writes. This sub-type of thick-provisioned virtual disk supports clustering features, such as fault tolerance.
For data security reasons, eager zeroing is more common than lazy zeroing with thick-provisioned virtual disks. Why? When you delete a VMDK, the data on the datastore is not totally erased; the blocks are simply marked as available, until the operating system overwrites them. If you create an eager zeroed virtual disk on this datastore, the disk area will be totally erased (i.e., zeroed), thus preventing anyone with bad intentions from being able to recover the previous data – even if they use specialized third-party software.
Read the entire article here, Thick and Thin Provisioning for VMware Disks: What is the Difference?
via the fine folks at NAKIVO.