You're teasing, of course, but it shows the real problems. To take you up on that with a dangerous example that reinforces the point: To add a disk to an arra

You're teasing, of course, but it shows the real problems. To take you up on that with a dangerous example that reinforces the point: To add a disk to an array whose used space is less than the capacity of a single disk, you can (DON'T DO THIS, IT'S DANGEROUS) (1) remove a disk from the array (it's degraded now) (2) reformat the single disk, put all data on there (3) create a sparse file with the size of one disk (4) create a new array with N disks, in place of the temporary disk use the sparse file as a device (5) remove the sparse file (the new array is now degraded) (6) bring the new array up, copy all data from temp disk on it (7) replace the sparse file with the temp disk (8) copy files around to make them re-balance Congratulations, you've now grown your array, and put your data seriously at risk in the process! :)