I've scoured the Internet in search of an answer to this question, and as usual with OSX-related topics, I often don't find any deep-dive technical explanations sufficient enough to feel confident doing dangerous things.

Here is my question: I have a Mac Pro, running OS X 10.6.2. I have, as my main root/boot disk, a RAID 1 volume called "Mirror1". Mirror1 is comprised of two 1 TB disks. Mirror1, however, is fixed at 640 GB. That's because, I originally took a 640GB disk, bought a terabyte disk, mirrored it (using diskutil appleraid enable), when it synced I removed the 640GB and replaced it with a second 1 TB disk, and synced again. Voila! A single 640 GB replaced by two 1 TB disks in a mirror.. Actually, no. There's still something missing from the equation: Mirror1 needs to be expanded from 640GB to 1 TB to match the partition sizes on each of those disks.

How do I do this?

Perhaps the diskutil output will help:

-> diskutil list
/dev/disk0 
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      GUID_partition_scheme                        *1.0 TB     disk0
1:                        EFI                         209.7 MB   disk0s1
2:                 Apple_RAID                         999.9 GB   disk0s2
3:                 Apple_Boot Boot OSX                134.2 MB   disk0s3
/dev/disk1
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      GUID_partition_scheme                        *1.0 TB     disk1
1:                        EFI                         209.7 MB   disk1s1
2:                 Apple_RAID                         999.9 GB   disk1s2
3:                 Apple_Boot Boot OSX                134.2 MB   disk1s3
/dev/disk2
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      GUID_partition_scheme                        *640.1 GB   disk2
1:                        EFI                         209.7 MB   disk2s1
2:                  Apple_HFS Mac Disk 2              536.7 GB   disk2s2
3:       Microsoft Basic Data BOOTCAMP                103.1 GB   disk2s3
/dev/disk3
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:                  Apple_HFS Mirror1                *639.8 GB   disk3
-> diskutil appleraid list
AppleRAID sets (1 found)
===============================================================================
Name:                 Macintosh HD
Unique ID:            1953F864-B474-4EB6-8E69-41834EBD0247
Type:                 Mirror
Status:               Online
Size:                 639.8 GB (639791038464 Bytes)
Rebuild:              manual
Device Node:          disk3
-------------------------------------------------------------------------------
#   Device Node       UUID                                   Status
-------------------------------------------------------------------------------
0   disk1s2           25109BAE-5697-40EA-B612-0217851444F7   Online
1   disk0s2           11B83AB0-8148-4DB6-8761-DEF08C855F8D   Online
===============================================================================

Thanks in advance.