I would also like to know the answer to this question. If your hard drives are still working properly and they are in a RAID config why not wait till one dies? When it dies the hotspare will take over. Replace the bad drive with a new one and it should rebuild itself. From the way I was told that is what happens.
There is no official sanctioned method to do this.
Unofficially, I'd do exactly what you say. Go into the configuration GUI, mark a drive offline, then replace it and let the RAID rebuild onto the new drive.
However, because I'm paranoid, I would only ever replace a drive with the same manufacturer, model, and firmware. I've seen far too many weird behaviors when having mixed drives in an array.
I think that is the method I will have to follow. I was smart enough to purchase replacement drives at the initial point of purchase, so I do happen to have a full 6 disk replacement set.
I just find it interesting that there isn't a more by the book way to do it from Intel.
I would do a full backup, replace all drives and create a new array, and then restore the data. If you replace hard drives one by one it means you'll need to rebuild your array 6 times, which is quite risky. If a hard drive fails during the rebuild, or even a hard drive has some bad sectors, data loss may occur.
From theory Dan_O's method shoud work although there are the concern's indicated by Edward. Rebuilding an array is risky in and of itself. A valid backup is the best possible way to do this. Plus it would save you a lot of time. Because of the risks involved, Iintel hasn't tested this.
One thing to note, after you replace all your 400GB HDDs with larger HDDs, the array size will still be the same as before. The rebuild will just grab the original "disk" size from the new disks during the rebuild.
You can use the online expansion feature to increase the array size to use all the space of the new HDDs. See the software user's guide for the SRCS28X for information on online expansion.
I checked this in our lab and I made a mistake. My explanation included a feature called Virtual Disk Resizing, where you can increase the size of a virtual disk using unsused space in an array. This feature is not supported on the SRCS28X. Online expansion is to add NEW HDDs to the array to increase the capacity, i.e. adding another same size disk to a RAID 5 array to get additional storage space.
After replacing and rebuilding with larger disks, the virtual drive size will be unchanged as we know. You can, however, use the extra space to create another virtual disk using the "new" unused space.
Sorry for any confusion.