RAID1, a failed disk and performance

[Chad Morland]

What happens in terms of performance when a drive in a RAID1 system
fails? Will disk access be slower because it attempts to read/write to
a failed disk or will performance be faster because it doesn't need to
do half the work it usually does? I couldn't really find any online
resources that deal with performance levels when there are failed
drives present in a RAID array.

-CM