Hu's Blog

By now there have been a number of good articles and blog posts that help explain the concept of thin provisioning. Some of the better ones have been posted by Tony Asaro and Marc Farley.

Most of the posts are about the benefit of reducing allocated but unused capacity.

There are some other benefits that should not be over looked.

The HDS approach to thin provisioning is to create a storage pool (Hitachi Dynamic Provisioning or HDP pool)which contains many logical devices. Capacity is allocated to “thin” volumes from this pool in units of 42 MB pages which are sliced across all the logical devices in the pool.

A storage pool can consist of tens to hundreds of logical devices. A page then consists of a wide stripe that spans tens to hundreds of logical devices which can be used to support an I/O request. This can have a dramatic increase in performance. It will also reduce the administrative effort that is required to tune volumes that are allocated to a limited number of logical devices since the volume will be automatically striped across all the logical devices in the storage pool.

Some users may even opt to assign one volume to one storage pool, just to get the performance benefit of wide striping, and not worry about the allocated but unused space.

The USP can support 32 storage pools today with plans to increase it in the future.

Hitachi Dynamic Provisioning can be viewed as two products, a thin provisioning product as well as a wide striping product for automated performance tuning..