Daily Archives: March 9, 2012

Linked Clones: Lab Manager vs vCloud Director v1.5

One of the big “features” added to vCloud Director that allows it “parity” when compared to the outgoing Lab Manager is the re-introduction of Linked Clones.  These Copy-On-Write (CoW) disks provide for VMs that are actually little more than differencing disks from a base disk.  Using Virtual Desktop Infrastructure (VDI) solutions, this is common to preserve disk space for all of your XP/W7 desktops you are spawning and allows you to better utilized small, expensive SSD drives.

Well, in LM and vCD, it is supposed to save space too. One beef I have with the current implementation in vCD is that it is actually worse when compared to LM.  The root of the issue, you see, is that in Lab Manager you could cleanly create a VM from a template, this would stay thin provisioned and it would act just like a classic VM, no linked clones and no CoW.  Well, in vCD you always get a linked clone no matter how you provision the VM if your Org has fast provisioning enabled.  This is also true for consolidations, where in LM you get a clean VM as result and in vCD you continue to get a linked clone, chain length of one.

In the long run, this is going to negatively impact disk space utilization.  As you are forced to always write to the differencing disk with Linked Clones, LM actually offered a nifty hybrid approach that allowed for overwriting the base disk when the VM was freshly provisioned or freshly consolidated.  This is a step backwards that I hope VMware will address.