Thin provisioning sure sounds like a good idea, too bad that over time the storage system can’t tell what is actually unused space. Without this ‘knowledge’ the storage system cannot reclaim the unused space and this renders the process of thin provisioning practically useless.
With a thin provisioned volume what you really end up with is an ever increasing high-water mark being set on the used space in your volumes. The problem is that the operating systems that are using the storage system (ESX in my world) don’t tell the storage system what they delete or mark as free space. Without this communication between the hosts and the storage system, thin provisioning is only a poorly implemented good idea.
There are ‘hacks’ out there that will go and write zeros across the LUNs. By writing zeros to large sections of the LUNS the storage system can tell that the space is unused. But, if you are going to implement a feature of your storage system you shouldn’t have to rely on a hack to make it really work. Seems more than a little deceptive to me. I am curious how others are dealing with the thin provisioning fallacy.
