We have a Linux environment on ESX 3.5 u2 so have been very keen to find a way to use the Hot Extend feature. I’ve been searching the net for a while for a method but found nothing so yesterday I asked a VMware guru about doing this with Linux. He gave me the following response:

“I don’t know exactly what feature set we have in 3.5, especially in the
storage area. However, I would imagine extending disks requires
re-attaching to the storage layer in Linux, which means at least an
unmount and re-mount. Typically, Linux won’t reprobe LUNs unless you
remove the driver module and re-install, so you would need a root FS on
a different storage type (Buslogic or IDE), and LSI Logic as a kernel
module.

Since dropping your entire non-root storage offline will take out any
active processes working on that (they must be stopped, or you can’t
unmount, and thus can’t remove the module), I would imagine this
hot-extend feature is not much better than a reboot, certainly not as
useful as PCI hot add/remove, which I believe we are adding in our
upcoming 4.0 release. With PCI hot add, a new controller can be
hotplugged, which truly allows you to add storage on demand with zero
downtime. I don’t know if you can add LUNs on demand, it would be a
driver dependent issue”.

So I think that gives me closure on the possibility… it’s just not going to
happen with Linux, at least for the moment.

Cheers,
Bruce

You are right that the functionality of extending VMDK files has always been ESX for a long time and that a helper VM can even do a boot vmdk, but the point of the article was more to show point out the hot extend functionality.

This functionality was introduced with ESX 3.5 Update 2 and admittedly builds on existing functionality, but now allows this functionality to work whilst the VM is running.

Thanks for you comment

ie: vmkfstools -X ##