VMware vSphere Thin Provisioning dramatically increases virtual machine storage utilization by enabling dynamic allocation and intelligent provisioning of physical storage capacity.
VMware vSphere Thin Provisioning gives you higher utilization by letting you dedicate more storage capacity than the actual available capacity. Traditionally, application administrators estimated and requested capacity, keeping future growth in prospective. This over-provisioning of capacity resulted in unused space, similar to the problem of RAM over-commitment in the server space.
With Thin Provisioning operating at the virtual disk level, vSphere administrators gain the ability to allocate virtual disk files as “thick” or “thin” format. Thin provisioning of virtual disks allows virtual machines on VMware ESX/ESXi hosts to provision the entire space required for the disk’s current and future activities, but at first commits only as much storage space as needed to store data. It cuts out the space allocated but not used and grows as more data is stored in the virtual disk.
Thin Provisioning enables you to over commit the datastores and in doing so increase the storage utilization by cutting down the amount of space that is allocated but not used. VMware vCenter Server provides the visibility of space allocations, space used and issues alerts and alarms a thresholds to inform the vSphere admin of a pending out of space condition or excessive over-commitment percent.
VMware vSphere Thin Provisioning operates at the virtual machine disk (VMDK) level. When a VMDK file is allocated it can be allocated as either “thick” or “thin”. Thin means thin provisioned. For example, blocks in the VMDK file are not allocated and backed by physical storage until they are written during the normal course of business. Note that a read to an unallocated block will simply return zeroes, but not back the block with physical storage until it is written.
Thin provisioned VMDKs are created more quickly and optimize the space usage. Once all of the thin or sparse disk’s blocks are allocated, they are not different from a thick disk.
- Interoperability.The complete operating system and hardware independence allows vSphere Thin Provisioning to connect and provision any tier of storage independent of connectivity.
- Thick to thin migration. Leveraging VMware Storage vMotion™ one can convert an existing thick format to a thin format.
- Alarms and reporting.Thin Provisioning is integrated with VMware vCenter™ Server. Therefore, you can provide reports and set thresholds to proactively manage growth and capacity. In vSphere 5.0, if an array is compliant, VAAI will automatically surface alarms in vCenter if the TP warning threshold (75%) is exceeded.
- Oversubscription protection. Thin provisioning can lead to oversubscription. Manage oversubscription by Storage vMotion (which enables dynamic migration of VMDKs) or VMFS volume grow (which provides the ability to dynamically increase the size of your datastore.) Oversubscription issues are also avoided in vSphere 5.0 with VAAI compatible arrays which automatically surface alarms in vCenter if the TP warning threshold (75%) is exceeded.
- Dead Space Accumulation. Thin provisioning can also lead to dead space accumulation whereby the deletion & movement of files and VMs is not reflected correctly on the array, and this free space is never reused. vSphere 5.0 introduces a new feature for handling dead space accumulation whereby the VMkernel can now tell the storage array that space is now free and should be reused. This is available on VAAI compliant storage arrays.
