Thanks for the input. :) I have not been clearing bad blocks yet because by now I figured out we have some damage in the Exchange database. The server is still online and functioning but we get Exchange database errors in the eventlog since the bad block message started. This is also seems to be the reason we cannot make a backup. However I have been able to export all data to pst files and copy all fileshare data. We already received new disks to replace the bad ones. After that I am thinking about restoring the last backup and importing the exported data to recover our Exchange database. 
Hi, After a disk failure we had a message saying "The Virtual Disk has bad blocks. For more details, see the Virtual Disk Bad Block Management section in the Online Help.".  I want to clear them out but before I do it I wanted to ask whether there is any way to find out how many bad blocks there are and what data can be affected by clearing the bad blocks ?  Thanks.
Virtual Disk bad blocks