VMFS Block Size - Adjust on demand?

[arraya-halim]

I realize there is no way to change the VMFS block size without reformatting it. Since this is true, why is it that the VI client's Disk/LUN formatting process states:

"These values are adjusted by VMFS-3 file systems on demand."

You can even see this screen in page 109 of the VI3 Server Configuration Guide.

They are clearly NOT adjusted on demand because if you have a 1 MB block size and attempt to create a 500 GB VMDK via the VI client, it fails with a somewhat incorrect error message that there is not enough space available.

[jonhutchings · Accepted solution]

I think this is poor wording - I think they mean when you create the VMFS it chooses the appropriate block size based on the size of the VMFS. Once formatted, as you correctly state, there is no way for the black size to be changed, as far as I know.

[VirtualKenneth]

Is this statement still correct?

I can remember from my course that they said that VMware block size would auto adjust. I've tried creating a VMDK bigger than 256 GB (on a 1 MB blocksize formatted VMFS) but it gives me an error stating that it can't be bigger than 256GB.

I guess that in theory it should be possible to change the blocksize since tools like partitionmagic also do crazy things without re-formatting the disk.

Someone else who knows more about this?

[admin]

AFAIK you still need to reformat a VMFS volume to change it's blocksize.