expand database volume

Hi,

We need to have more space on our mailbox database volume, so we are adding
more disks to our SAN. Store database is on a RAID5 LUN. If we expand our LUN
with more hard disks, can the OS windows 2008 expand the volume in which
databses are stored. Also can I have a single RAID 5 configuration with
different capacity hard drives, example can I expand (add) the existing
4X300GB with 3X 500GB.

thanks
.

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