PowerEdge T410 need to install 2 drives

Can you share details on the storage controller and rail you created on these drives? Are the drives have RAID 1 or RAID0?

Below link have details on replacing physical disk. You need to have redundant RAID level to ensure there is no data lost. It is good practice to backup your data before carrying out any such maintenance tasks.

https://www.dell.com/support/kbdoc/en-us/000143539/poweredge-hdd-how-to-physically-replace-an-hdd-hot-swap-procedure?dgc=SM&cid=243909&lid=spr6153914739&RefID=dtw22_sm6153914739&linkId=146721776 

It's RAID5. There are 3 physical drives. 2 300 GB drives and 1 900 GB Drive. 

I am planning to replace 1 900 GB Drive and 1 300 GB Drive.  Again, those drives so GOOD and no issues. So wanted to be clear on the correct process to replace those 2 drives. 

Hi, thanks for choosing Dell. Please work with the 300GB. After rebuilding when you see the VD status as optimal, then start with 900GB for another rebuilding.

sorry for the late reply. i've had to wait for a week but I was able to install the 300 GB. It rebuilt the RAID and all looks good. Took another backup yesterday and so shut down the server. Then installed the new 900 GB Drive and didn't boot. Error "Foreign configuration found on adapter. Some configured disks have been removed from your system or are no longer accessible. "

so had to put the original 900 GB drive back and it booted up just fine. Should I have just installed the 900 GB while the server was on?

"Foreign configuration found" message will come when the disk which you inserted was previously part of a virtual disk and those metadata exist on the disk. You can go ahead and clear the foreign configuration. Once foreign configuration are cleared you will be able to use it as part of virtual disk

Yes I just installed the 900 GB drive as a hot swap and it starting rebuilding and now everything looks good. Thanks