Hello. I have a Dell PowerEdge R720 server. It currently has 12 900GB drives. The server is running Red Hat Linux.

• 2 drives configured with RAID 0 or RAID 1, can't remember. Virtual Disk 0.
• 10 drives configured with RAID 5. Virtual Disk 1.

Virtual Disk 1 only has one partition, /dev/sdb1. I want to increase the size of this disk. I want to add 3 more 900GB disks to the RAID 5 array. What are the steps to do this? I can access the iDRAC interface of the server to manage it. Here is what I've got so far:

1. Add the physical disks to empty slots on the server.
2. Access the iDRAC interface (or maybe the Ctrl+R utility when booting?) and add the extra 3 disks into the array. I'm not sure if I need to "delete" the array, or do I just "add" the slots to the array?
3. "Reconfigure" the array. After this step, I think the drive will now have the extra space.
4. In the OS, expand the partition to use the extra unallocated/free space. I know the steps for this part.

I do not want to lose any data on the RAID 5 array, and I want to avoid rebooting (I guess I could reboot if push comes to shove). My concern is with steps 2 and 3. Does "reconfiguring" the array delete the data? Also, do I need to unmount the (only) partition on the drive to add the disks to the array? Or is it done "live" or "online". Also, how much disk space will these 3 extra 900GB drives add to the array? Is there a simple calculation I can use to figure out how many disks I need to add X number of TBs, given the disks will always be 900GB?

I don't have access to the server right now, so I can't give more information on the RAID controller name and version. But just an FYI: we once replaced a failed drive by swapping it out with a new one without having to shut down the server. Maybe this bit of info can shed some light on the RAID controller.