I ran into the same issue as the other posters in this thread with SCVMM 2012 R2. All blades in the same chassis as shipped have the same Service Tag. It looks like Dell uses the Service Tag when generating the SMBIOSGUID.
We were having some issues with the MegaRAC on one of our blades in a remote datacenter, and weren't able to mount the Dell technician ISO that i've seen floating around elsewhere that has the asset tag modification utility. We are a Windows shop so the c6100 BMC tool was not an option either.
Fortunately, I was able to edit the asset tag using the windows build of
ipmiutil.
Install it following the instructions in the readme, and run the following command to change the service tag:
ipmiutil.exe fru -s %newassettag%
After running it, reboot, and the SMBIOSGUID will change.
I've been incrementing the last character/number on each of the other 3 blades & documenting what the old & new ones are in our asset tracking database. If we need warranty service on a blade we've changed we'll just switch it back to the original before sending it out.