MKguy wrote:
I can't find a source for that at the moment (think I saw it in a whitepaper), but I'm pretty sure that read requests against thin-provisioned or lazyzeroed blocks that haven't been written to on a VMDK will always return zeros and not the actual data of the physical disk this block is located on, so security should not be a concern.
That is correct. There will never be an possibility to read old data, everything has to be erased ("zeroed") and it is only a question of when: eager = do it at creation = lots of write IOs to the SAN, could take a long time to create the virtual disk, but best performance. Lazy = do it when it is needed = somewhat slower write access at new locations.
Long ago there was a "thick" which was without any zeroing at all, but that is no longer possible to create.