I'm building a server with a RAID5 array, based on a hardware controller. I want to be able to later add additional disks and have the array rebalance across all of the disks, enlarging the usable size. I also want to be able to later upgrade to bigger disks (one at a time, of course) and then expand the array to fill the entire drive.
These features are available in Linux software raid (md). I've also heard they're available in some hardware controllers. Currently, I own the Adaptec RAID 3805 card and the 3ware 9650se card. I'd prefer to use the Adaptec if possible, but I can't find if either of these cards offer this feature.
If they don't, are there other affordable (read as: sub-$600) RAID cards available that can accomplish this?
The 3Ware 9650se card has this in its spec-sheet:
That's exactly what you're looking for.
The Adaptec 3805 specifically states it provides "Online Capacity Expansion" in its 'specifications' tab HERE. This will allow you add more of the same size or larger disks 'live' but I'm not aware of any hardware controller that will will let you somehow grow the array with bigger drives, they usually take a 'smallest common denominator' strategy.