VM Types Explained
One of the first decisions in SAN storage provisioning is making the LUN decision: determining what RAID level for the LUN based on the application I/O profile to provision a physical LUN to ESXi. This task is usually done based on prior experience with the application or some help from vendor’s best practice guide.
The next step is to choose a suitable virtual disk format for VM’s virtual disk. Here are three formats of virtual disks:
Thin: In thin provisioned disks, the size of the VMDK (at any point in time) is as much as the amount of data written out from the VM. So if you provision a 1 TB virtual drive and the VM only wrote 200GB then the size of the vmdk on disk is 200GB. The key thing to note is that the storage is zeroed on demand and data written out.
Lazy Zero Thick (aka Flat): In Flat or Lazy Zero Thick format, the VMDK is provisioned and whenever a guest issues a write it is zeroed first and then the data is written. The size of the VMDK on the datastore is same as the size of the virtual disk that was created.
Eager Zero Thick: With Eager Zero Thick, the VMDK is pre-zeroed and assigned to the guest during provisioning of the VMFS volume.
One of the first decisions in SAN storage provisioning is making the LUN decision: determining what RAID level for the LUN based on the application I/O profile to provision a physical LUN to ESXi. This task is usually done based on prior experience with the application or some help from vendor’s best practice guide.
The next step is to choose a suitable virtual disk format for VM’s virtual disk. Here are three formats of virtual disks:
Thin: In thin provisioned disks, the size of the VMDK (at any point in time) is as much as the amount of data written out from the VM. So if you provision a 1 TB virtual drive and the VM only wrote 200GB then the size of the vmdk on disk is 200GB. The key thing to note is that the storage is zeroed on demand and data written out.
Lazy Zero Thick (aka Flat): In Flat or Lazy Zero Thick format, the VMDK is provisioned and whenever a guest issues a write it is zeroed first and then the data is written. The size of the VMDK on the datastore is same as the size of the virtual disk that was created.
Eager Zero Thick: With Eager Zero Thick, the VMDK is pre-zeroed and assigned to the guest during provisioning of the VMFS volume.
No comments:
Post a Comment