Thin Provisioning
Overview
Current storage management best practice introduces a lot of waste. Traditional LUNs cannot grow easily, involving a time-consuming and error prone process, particularly if the LUN is large. This encourages administrators to allocate a LUN size based on the expected growth 1, 2 or 3 years ahead. Similarly, a development team may request a LUN size far in excess of their immediate requirements. Once a LUN has been provisioned then that storage capacity becomes allocated and unavailable to other users. As a consequence 30%-50% of allocated storage may in fact be unused.
Thin Provisioning (some times known as "over allocation") enables storage administrators to create large virtual volumes but only consume the amount of capacity actually used by the data.
It is important to recognise that Thin Provisioning does not prevent storage shortages or their effects. If the physical storage is not available, regardless of the size of the virtual LUN, then the application performance may suffer or crash. Also, with many overlapping LUNs sharing the same disk pool, performance may degrade.
Thin Provisioning introduces an element of just-in-time management that benefits from good capacity management and the ability to free up or reallocate space at short notice. Vendors have built-in alerts to warn administrators when thresholds are being reached.
Advanced copy services can be made more cost-effective using thin provisioning especially where there is a low number of changes to the copied data. The amount of physical disk in the target site can be significantly reduced.
All the major storage vendors have versions of Thin Provisioning and it can be combined with
storage virtualisation, which significantly improves the potential storage utilisation benefits. It is expected that Thin Provisioning will become a standard feature of tier 1 and 2 disk subsystems over the next 3-5 years.
Key Deliverables
The big advantage of Thin Provisioning is the ability to reduce the amount of allocated but unused storage and hence the amount of storage purchased. This can apply to both spindles and subsystems
Since the virtual LUN and physical space are separate, additional physical storage can be added without altering the LUN or disrupting the application, making administration easier and faster
Thin Provisioning has the option to allow LUNs to dynamically expand to deal with demand spikes
When combined with advance copy services users can benefit from improved RPO at significantly lower licence and storage cost
Vendor Alliances
