How Can I Use Thin Provisioning Safely?

Thin provisioning is a great new technology that promises to increase storage utilization and lower both capital and operational costs. However, there are some dangers inherent to thin provisioning that storage and server administrators should be aware of.

Thin provisioning allows the storage administrator to present a larger logical volume to a host while only allocating enough physical array capacity to that volume to satisfy immediate needs. The array reserves a common pool of storage that can be added seamlessly to any thin-provisioned volume as the physical storage is needed by the host.

The primary advantage from the host perspective is that there is typically no downtime or administrative work required to recognize the new physical storage. The advantage from the storage perspective is allowing applications to set up file systems on large volumes without actually reserving all of the additional space on the array. This additional space is typically unused for long periods of time, yet cannot be shared with any other hosts or applications within the array.

Thin provisioning is a relatively new technology, and should be implemented with care. Current vendor software offerings for thin provisioning are not appropriate for most mission critical email or high transaction OLTP applications.

Where thin provisioning is appropriate (test and development environments, static and predictable production applications), the server and storage administrators must implement a robust set of monitoring, reporting, and alerting tools.Thin provisioning software allows easy volume growth, but it is typically not automated. As such, file system utilization alerts and reporting must be religiously watched so that administrators can intervene and add storage where necessary. Additionally, thin provisioning works on the assumption that all applications will not need additional storage at one time. This assumption allows for a smaller common pool of unallocated storage and leads to the higher utilization rates. If your environment needs to grow quickly across many applications, a thin provisioned array may not have enough capacity to satisfy the demands.