Linux Software RAID

[Jimmy Stewpot]

Hello,

Is it possible to grow Linux software RAID volumes after the initial deployment. For example can we have a RAID5 array with 3 drives and then add an extra drive later? Is the Linux software raid intelligent enough to move the blocks of data around to take advantage of the additional redundancy that we would have from 4 drives? 
I am guessing that if its possible it would be a two step process. One would be adding the drive into the software raid set. Then the second would be increasing the file systems size?

any feedback would be great.

Jimmy.