Hello,

regarding Raid configuration you also have to count in the time/cost of a rebuild.

If your smallest unit is 1 mirrored drive the controller only needs to read and write the content of 1 drive to rebuild the mirror.

If you have let's say a 4 drive raid 5 configuration the controller has to read the content of 3 disks to rebuild the raid array.

Now consider a SAN box having a raid 5 or a raid 0 with say 20 drives...

Reading the content of 19 drives to rebuild the array - how long will the array be degraded? When will the next drive fail?