Although the core issues with thin provisioning revolve around communication, it presents unique challenges to the storage array as well. We talked about granularity of pages, and the comments for that piece were extremely enlightening. Now let’s consider another key factor: Scheduling.
The most exciting enhancements in VMware vSphere 4.1 is the addition of vStorage API for Array Integration (VAAI). This new API allows VMware ESX to offload storage processing functions to capable storage arrays, reducing the workload on the server hardware in introducing new and exciting possibilities for performance and efficiency. VAAI in ESX 4.1 includes three separate capabilities: block zeroing, full copy, and hardware assisted locking.
Although I consider it the main stumbling block for thin provisioning, communication (or lack thereof) is being addressed with metadata monitoring, WRITE_SAME, the Veritas Thin API, and other ideas. But communication isn’t the only issue. Let’s talk about page sizes. You’ll often see vendors tossing this “softball” objection at their competitors, claiming that their (smaller) page size makes for more-effective thin provisioning. And that’s true, to a some extent.
It’s been a slow week (the holidays) and a crazy one. I’ve started pouring out the thin provisioning series, with 10 posts so far, as well as launching a new video “talk show” about enterprise IT. And I’ve got a new post over at SearchStorage, too. Whew!
If WRITE_SAME can be a semaphore for thin un-provisioning, what about TRIM? It sounds like a perfect fit, and has wider implementation to boot! Let’s take a deeper look.