By default, VMWare ESX server uses a 1M block size which limits
you to having a maximum of 256GB in any single virtual machine. By
changing the block size of your vmfs partition, you can increase
the maximum amount of disk you can have. A 2M block size yields a
maximum disk size of 512 GB, 4M yields 1TB, and 8M yields 2TB. There
is no support for anything larger under vmfs3. Vmfs2 had a maximum
block size of 16M, but that has been removed in the vmfs3 specification.
To change the block size of a vmfs filesystem, you need to use vmkfstools to reformat the partition. The command is:<code>vmkfstools --createfs vmfs3 --blocksize 8M vmhba0:0:0:3</code>
It is important to note that like any other formatting procedure, this
will destroy any data on the partition, so make sure you move your data
before you do this. The “vmhba0:0:0:3″ is where you specify which
partition to reformat. According to the VMWare server configuration
guide, the format is:
vmhbaA:T:L:P format, where A, T, L, and P are integers
representing adapter, target, LUN, and partition number respectively.
The partition digit must be greater than zero and should correspond to
a valid VMFS partition of type fb
For example, vmhba0:2:3:1 refers to the first partition on LUN 3, target 2, HBA 0.
If you’re reformatting a current vmfs filesystem just to increase
the blocksize, you can get that information from the storage section in
the configuration tab of the Virtual Infrastructure Client.
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