VMDK Thin Provisioning

[MilesD]

We have a new NetApp 3040 and are currently creating the Windows templates for xp, windows 2003. The final VM's will be stored on 300gb VMFS volumnes using iSCSI and shared across multiple hosts for HA / Vmotion.

The NetApp best practises recommends using the vmkfstools -d option to thin provision the VMWare disks to ensure maxiumum usage of disk space. Given the extra space will be handy, is there a risk of these getting fragmented and slowing down on growth? What are the best practises?

[kix1979]

Yes, they can get fragmented if you do this way. I really find it hard to believe that they would recommend that. The best way is to preallocate the whole disk and have it zero out all of the space. This will lead to the best performance. Any time you have to expand the space on the fly will lead to a degradation in performance.

[MilesD]

I guess they are presenting it as more of an option really to help save space if required. In their best VMWare practises guide, page 23 @ http://www.netapp.com/library/tr/3428.pdf.

But does anyone really use it and has it caused any major issues? Will probably go for zero thick as it sounds the safer of the options.

[kix1979 · Accepted solution]

No major issues, you just have to use a SAN tool to defragment the LUN from time to time. Other then that, if you are low on space it is a fine way to go, just realizing there is a slight performance hit.