When Things Go Wrong
There are two kinds of failure with RAID systems: failures that reduce the resilience and failures that prevent the raid device from operating.
Normally a single disk failure will degrade the raid device but it will continue operating (that is the point of RAID after all).
However there will come a point when enough component devices fail that the raid device stops working.
If this happens then first of all: don't panic. Seriously. Don't rush into anything; don't issue any commands that will write to the disks (like
mdadm -C ,
fsck or even
The first thing to do is to start to preserve information. You'll need data from