Understanding, Zeroing, Lazy Zeroed, Eager Zeroed, and Thin Provision concepts in VMware vSphere.

Or, VMware Disk Provisioning Concepts about Lazy Zeroed, Eager Zeroed and Thin Provision.

Or, Lazy Zero Vs Eager Zero Disk Provisioning.

Or, Difference between Thick Provision Lazy Zeroed, Thick Provision Eager Zeroed, and Thin Provision Disk Provisioning.

Zeroing

Before the VM can actually use the allocated drive space, there are some operations that take place on ESXi host level. When you allocate a disk space from your Datastore, Datastore also maintain itself to allocate that amount of Disk space with clean/formatted sectors.

This disk sectors cleaning process is basically referred as Zeroing term. As you do disk formatting at Guest level to make it ready to use, the same task is performed by ESXi Host at Datastore level when you add any partition/disk to a VM from any Datastore.

Thin Provisioned Disk: Allocate and zeroed on first write. When you create a disk with thin provisioning method, it only writes a small amount of metadata to the Datastore where it resides. When the write operation is performed, vSphere first updates the allocation metadata of the VMDK, then zeros out the blocks, lastly it writes the data. Thin provisioned VMDKs have the lowest performance logically at some points.

Once the Zeroing is completed for allocated disk blocks, almost all disk types performs equally.

Thick Provisioned Lazy Zeroed Disk: Allocate in advance and zero on first write. Do nothing to empty blocks, it zeros all the blocks at first access... Provisioning of this disk type is little faster than other disk type. Performance of this disk type is slower than Eager Zeroed Disk type and it is not supported for clustering.

Example: If you have 10GB disk size and having only 5GB data in it, then 5GB will be zeroed at first access, rest 5GB will be left.

Thick Provisioned Eager Zeroed Disk: Allocate and zero in advance. Writes 0 to empty blocks. Write is performed on whole allocated disk.  Means, its pre-zeroing all the blocks on the disk. Performance of this disk type is better than all others but provisioning time may take little longer than other disk types. It also supports clustering features.

Example: If you have 10GB disk size and have only 5GB Data in it, then 5GB will be used and rest 5GB will be written with 0. No further Zeroing is required while any write operations.

Cheers, Please write me back if you have any query or feedback on this..

Understanding Thick Provisioning and Thin Provisioning in VMware

Or, Difference between Thick Provisioning and Thin Provisioning in VMware

Or, How Think Provisioning and Thin Provisioning works in VMware

Descriptions: Thin Provisioning disk allocation method in VMware vSphere is one of the cool feature to use your storage to a limit beyond the storage capacity limit… There are some pros and cons of each provisioning method whether it is Thick or Thin but it’s all depends on your requirement and criticality of servers and how you want to use it.

e.g. For database servers, I rarely think of allocating Thin Provisioned Disk. Because, Database log files and even Database can increase anytime drastically and if you don’t have enough free space on the respective Datastore, This VM will go in Answer mode (its equal to down till the time you fix it).

Thick Provisioning: This provisioning refer to disk provisioning method where all the allocated disk space is occupied by the Virtual Machine.

Example: When you allocate 40GB drive space to a Virtual Machine with thick provisioning method, it reserves all 40GB allocated disk space from your Datastore. Even if the VM is having 10GB of data inside that drive, it will take complete 40GB space from the associated Datastore. There are further two type of thick provisioning, Lazy Zeroed and Eager Zeroed.

Thin Provisioning: This provisioning method refers to disk provisioning method where only used space is occupied by the Virtual Machine.

Example: When you allocate 40GB drive space to a virtual machine with thin provisioning, it does not reserve the complete 40GB allocated disk space from your Datastore. If your VM is using only 10GB of out of 40GB allocated drive space, then thin provisioning helps remaining free 20GB disk space to be released from that particular VM. Means, no matter how much drive space you have allocated for your VM, it will utilize only what it required.

You can try it by assigning 40GB drive space with Thin Provisioning method to any VM even if you have 30GB of drive space free in your Datastore. It will allow you to do so.

Reference screenshot-1: I have 20GB free space in Datastore and adding a Disk with 40GB capacity to my Test-VM-1 with Thick Provisioning Method.

If you will dare to go with this option, you are going to end up with below error.

Reference Screenshot-2: I have 20GB free space in Datastore and adding a Disk with 40GB capacity to my Test-VM-1 with Thin Provisioning Method.

 Cheers, please write me back if you have any query or feedback on this…