A drive failed on a Dell SAS 5i controller - see controller bios screengrab: http://imagebin.ca/view/SkZbszA.html

The primary is a 160GB 10k sata drive.

I added a 250GB 7k rpm drive in the hope that the array would rebuild onto this drive. This did not happen. (assuming that the controller would just operate at the speed of the slowest drive)

The controller could see the new drive, but it didn't automatically rebuild the raid1 onto this drive. (my assumption is that it did not do this rebuild as the drive sizes are different).

There was an option to add the new drive to the existing raid1 array - but when I tried this a message appeared stating that all data on the array would be lost. (I didn't get a screenshot of this message, I will later)

Should the SAS 5i allow me to rebuild the array onto a larger drive?

Is the option to add the drive to the array the right way to go?

Many thanks!