Here is a link to the support matrix for your MD1220. If you look on page 10-16 it list out all the support hard drives and their Dell part# as well. http://downloads.dell.com/manuals/common/md1200_md1220_supportmatrix_en-us.pdf
Please let us know if you have any other questions.
Dell | Social Outreach Services - Enterprise
Download the Dell Quick Resource Locator app today to access PowerEdge support content on your mobile device! (iOS, Android, Windows)
Get Support on Twitter @DellCaresPro