  By design, the system SHOULD run with only one disk, with or without removing the failed one.  However, in some circumstances, maybe especially with cheap controllers like the ones that shipped with the R210, drive failures can affect the entire system. Some things to try (I, personally, would try them in this order): 
Dear Experts, One of the hard drives for the Dell PowerEdge R210 server are broken (there are 2 x 1TB Disks ([URL] connected via the SAS controller. What would be the correct way to restore the Server in working order, given that one of the two disks seems to be fine (at least the disk tests show no errors so far)? Do I just purchase the same disk model and replace the broken disk?  Thank you in advance for your assistance! With Best Regards, Karlis [URL]
One of two disks for PowerEdge R210 broken