Hi
Do you want to replace three disk in the RAID set or do you want to add 3 disk to your raid set. Both can be done on a DL380 with the extend\expand option in the Array config utility.
What's the RAID level ?
What is the operating system ?
How many partitions do you have? eg Primary extended etc.
I have expanded RAID arrays on DL380's with both Netware 5.1 and Windows 2003 SP1 a number of times. I had one failure years ago on Netware 5.1 which I put down to a early BIOS revision, so make sure you have the latest BIOS for your controller and of course a good backup. You can even convert for say RAID1 to RAID 5 if you have the right amount of disks without losing any data. When playing with arrays when it goes wrong it really goes wrong and your vendor will just tell you to restore.
There are a number of other threads of this forum or the Compaq forum which you can read as well.
I have found different versions of the Array config Utility where there is different wording of the Expand and extend options, but basically they do the same job.
There are also a number of after market products which make it resizing RAID arrays and OS partitions simpler, but it can be done with existing utils for Netware and Windows.
Anyway let us know what you have any we will try to help out.
Regards
David