from:
http://servalpaul.blogspot.com/2013/05/diskwarrior-error-36-2747-hardware.html
Everything lit up correctly and the Drobo (2nd generation) showed up in the Drobo Dashboard, but the drive would not mount and Disk Utility did not help.
DiskWarrior was giving me the (-36 2747) “hardware failure” error so I entered the following in Terminal to allow DiskWarrior to rebuild the directory.
ps -ef | grep fsck_hfs
then
sudo kill ####
where #### is the 2nd number from the left in what Terminal spits out at you.
I hope this helps someone else who needs to rebuild their directory with DiskWarrior.