What is VAAI?

This is more of a post for myself going over VAAI before I take my VCP 5 exam soon, so I wanted to get some pixels on the screen about VAAI.

VAAI stands for vSphere Storage API’s for Array Integration.  It has been around since vSphere 4.1 and is used to ‘pass’ storage related functions to the array rather than being performed by ESXi.

Some of the benefits from using VAAI are:

Hardware Accelerated Full Copy tasks such as power on VM’s or cloning VM’s are more efficient.

Hardware Accelerated Block Zeroing if you create a disk using ‘Thick Provisioned’ Lazy Zeroed, then the array will take the responsibility to write the zero’s instead of ESXi.

Thin Provisioning perhaps the most important one.  ESXi5 know’s that a LUN has been thin provisioned and can reclaim dead space.  Why is this important? Well imagine you put a 4GB ISO file onto a production VM to install a third party piece of software. After the software has been installed, you delete the ISO file, but how does the array know that the 4GB of space can be reclaimed? The operating system doesn’t tell ESXi5 or the array to reclaim the space as it’s no longer used, instead it comes from the T10 UNMAP command.

How do we know if our SAN is VAAI supported? If you go to Storage > Devices and look at the Hardware Acceleration Column, you are looking for ‘supported’.

We commonly use HP SAN’s and different levels of SAN Management Software will have VAAI support for example HP P4000, need SANiQ version 9 or above to support VAAI (9.5 is out).

Naturally, as we are all IT professionals we regularly update the firmware on all of our devices!

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