What happens if raid gets broken?

[Roland]

Hi,

What happend if for example 1 disk of a mirror raid gets broken, has bad 
sectors? Will there be an appropriate error message and will the metadata be 
changed? 
I am running dmraid with a hpt37x mirror (raid 1) on 2.6.10 debian amd64. When 
I copy some large files onto the raid, my computer "freezes" and I dont get 
any message in syslog or dmesg. I load dmraid in verbose mode and also have 
enabled debug symbols but dont see any error message. 
Whats wrong? Is this a problem of the device mapper? Any Idea?

thanks
Roland