"Is there a high risk of loss on the good drive (understood we can't hold you to this) if we manually rebuild by right-click>select rebuild?" There is no more risk in starting the rebuild manually than letting it start automatically.  It is just giving the controller permission to use the disk for the rebuild in the event it did not start it automatically when the drive was inserted - for whatever reason. "It has the original firmware that came with the box.  We have been told by Dell previously that updating firmware may resolve this type of issue, but they always warn that total data loss is a real possibility.  Being an older server, we elected not to risk this until we can replace the server." Firmware is the most likely reason it did not rebuild automatically.  Dell must tell you that data loss is a possibility to relieve themselves of liability.  Ever see Dumb and Dumber?  "One in a million."  "So, you're saying there is a chance."  Hundreds, maybe thousands of PERC firmware updates and I have never seen "data loss" occur from updating the firmware.  However, I understand your hesitation.  
We have a RAID0 with two drives, 0:0 & 0:1.  Drive 0:1 failed.  The light on the drive is blinking red, and array manager indicates it is in a failed state.  We replaced drive 0:1 with a new drive.  This server supports hot-plug drives, so we pulled the failed drive while the server was running, and the inserted the new drive.  The new drive blinked green temporarily, and then turned red.  We checked the status of the drive in both Array Manager and the SAS Bios, and see the status of the drive as failed.  We were under the impression that this drive is hot swappable, and should automatically rebuild.  Can someone please advise how to check if automatic rebuild is enabled and/or how to manually rebuild.  Important!  We cannot do anything that will risk losing data on the existing drive in the array (0:0). Thank You in advance for helping us out!!!  
!!!PowerEdge 1750 Raid0 2HDD Help Needed!!!