Extend Raid5 with a new HD (HP DL380 G3)

Assuming you're using the HP controllers: You'll need to reboot, hit whatever the key is to get into the RAID controller, add the new drive to the container, and then wait for the array to rebuild. When you boot up, you'll need to expand the partition.

It's fairly simple once you start doing it, but schedule more downtime than you need and take a backup first just to be safe. That's just good practice any time you're messing with the storage layer.

If you're using software raid or a non-HP controller... well, you're kinda on your own, kid.

If you installed the HP Array Configuration Utility CLI, you should have a hpacucli.exe program which allow you to add your disk without rebooting your server.

Not sure how it works on windows but it does without problems on linux.

It should be something like

hpacucli ctrl slot=0 array A add drives=1I:1:4

then extend the logical drive

hpacucli ctrl slot=0 logicaldrive 1 modify size=max