I'm afraid that at this time this will be a rather vague explanation of my problem, but this may set me in the right direction.

Currently I am running an HP Proliant machine with a Smart Array P400 Controller for raid 5 with 4 146gb disks to keep our code safe from any one drive failure. In the near future I'll have to expand the 411gb I have for data (I'll be shooting for over a terrabyte when the day comes).

From everything I have read I believe this setup to allow me to add some drives to this array and nondestructively grow my array with an HP utility and then nondestructively use a program like GUN Partd or Partition magic to increase the end point of my reiserfs partition.

I have two empty slots left out of 8 (2 are being used for one array, 4 four the raid 5 array, and then the two empty slots).

Does this sound possibly? Or does it sound likely that to add new space I'll have to recreate the array?

you can grow the array with the HP utility, though if you do lose data HP will probably deny responsibility, so backup everything before you do.
however, after you grow the array, the partition sizes will remain the same, so you'll have to grow the partitions using LVM (if you implemented it) or something like partition magic. this is even more dangerous.

So at this point in theory after using HP to grow the array (which will be viewed as the single disk by the OS) I'll have unallocated space and in theory using a disk partition program to move the end point should work...but there is danger in the fact I could lose all my data (which I will backup)?

But it SHOULD work.

Actually, it appears that I will be good to go with using the resize_reiserfs utility.

Here is a brief summary of how it works.

In a quick test it works pretty fast.

http://www.eng.uwaterloo.ca/twiki/bi...ResizeReiserFS

I was also running HP Proliant H/W (DL 360 G5) with an attached MSA500. Let me tell you, using the HP utility worked, but don't expext it to be fast. It took around 48 hours to grow ~ 300Gb. I had added 1 x 300Gb SAS drive to the MSA. I did not have a lot of faith because of how long it was taking, but it worked.

One thing to point out to you. Interestingly enough, the HP utility counted up the number of new cylinders differently than did the Red Hat ES4 LVM. That was a nightmare to find the sweetspot. Good Luck to you.