S3 Ltd

Doing More With Less - Thin Provisioning

07/05/09 | in: General

The concept of thin provisioning is really very simple; by being smarter in the way disk space is allocated less disk drives are needed. Consequently less power and space are needed, significant cost reductions are made and the corporate social responsibility requirement to produce a lower carbon footprint is satisfied. It looks like an all round winner!

So what is thin provisioning? Normally an application is allocated disk space in the form of a LUN. Administrators will typically allocate a LUN size with sufficient physical disk space to meet the application’s immediate needs and its potential growth. As the administrative work load involved in increasing LUN sizes regularly is substantial it is normal for a LUN size to be set at a level that will meet the application’s requirements for 2 to 3 years.

Thin provisioning allocates a virtual space in which the application thinks it has, say, 2 terabytes but if, for example, it is only using 500 gigabytes this is all the space it actually gets. Additional space will be allocated on the fly, as required. In a normal environment the difference between actual usage (in this example 500 gigabytes) and the amount allocated to the LUN (2 terabytes) is filled with zeroes and carried as overhead until it is full. When that happens the administrator will allocate additional LUN space to last for another 2 or 3 years or whatever is the operational norm. So the bottom line is that thin provisioning optimises the use of available disk space.

Savings are made in a number of areas. For example:

  • Capacity usage ESG note that typically storage capacity utilisation is boosted by 60 – 80% through the use of thin provisioning.
  • Administration – Let’s say that LUNS are allocated for three years and there are 150 volumes. That means on average one volume a week has to be changed. Thin provisioning eliminates this effort.

Expanding volumes often implies downtime with the consequent impact on productivity. Thin provisioning eliminates this requirement.
Power consumption – Disk arrays are large power consumers. Reducing the physical space requirement will also bring down the electricity bill.
Thin provisioning was first popularised by relatively small companies like 3PAR, Compellent Technologies, LeftHand Networks (now owned by HP) and Pillar Data Systems on the hardware side, as well as SAN software developers such as DataCore and FalconStor. Most major storage array suppliers, including NetApp, EMC, HDS and IBM are now onboard with thin provisioning.

Thin provisioning has a major role to play in achieving the goal of doing more with less. Next time we will look at some suppliers and what some of the downsides might be.