Hello Mhmood Hamooda, When you added your MD1200 to your MD3200 did you power down your MD3200 first then add the MD1200 & power it on first then wait about a minuet then power on your MD3200? Also what is the current version of firmware that is running on your MD3200? Sometimes I have seen that if not running a current version of firmware that an MD1200 when added is not seen correctly. Please let us know if you have any other questions.
I have PowerVault MD 3200 and I expanded it by PowerVault MD1200 When I connect MD 1200 it doesn't show up on Storage Manager and I get error message in Event log says that "Physical physical disk has unsupported capacity" message is repeated by each slot no. My MD1200 consist of 12 Dell Hard Disks (SAS  12Gbps - 512e - RPM 7.2K - 6 TB) I even tried to put single HD with 6 TB but didn't work out so, I know that it seems unsupported Hard Disk capacity but, having read the specification sheet for MD1200 it confirm that it support up to 10 TB. Ref. ([URL] Quote "3.5” 12Gbps SAS: HDD 7.2K NL-SAS 512e – 6TB, 8TB, 10TB"   Much appreciated your assist...  
Physical Disk Problem