I run into this issue to often.
I always have to reach into the back of my brain and “drain” it, the solution, out, as it were.
So here, let’s talk about a few notes. First off, if you have a server invest the extra couple hunderd dollars in iLO or DRAC devices (or what ever they will be called in the future)!! It might not seem important until that 3am call for your engineer. Heck it might just seem like overhead after you have many installed but not used over a long period of time … until that one day. That one faithful day. Remember … I told you so … should you decide it’s not worth it to get them. There are not many out there that can find the information buried in their subconcious, nor is documentation, that can be found if you search for it, very clear on the solution. I’ve experianced vendor’s support techs wiping whole servers because they didn’t understand the fix.
First let’s get to some of the reason you have landed here.
You have a RAID code on a drive saying soemthing to the following effect:
SCSI CDB sent 04 00 00 00 00 00 00 00 00 00
or perhaps it is a similar error code in look of:
SCSI CDB sent 03 00 00 00 00 00 00 00 00 00
Or a plethora of other codes. For instance you will find the popular SCSI adapter manufacturer Adaptec’s Sense Code list here.
What we will discuss further here is how to recover a Dell implimentation with a Sense Code of 04 00 00 00 00 00 00 00 00 00 – The drive is not ready and the error is not reportable.
First in this case you probably have lost a RAID 5 container. There may be multiple drives in a failed or degraded state. Degraded I can help you here…more than one in a RAID 5 with 4 drives … I can not help with these steps.
NOTE: Though I may be able to help you recover your data at this point you need to be aware that a least a portion of the data will end up being corrupt.
Now, if you know how to boot to the RAID utiility we are in shape. If not, try contacting me directly and maybe I can help walk you through your issue. Hey, I am a consultant by trade after all. 
- Once you have hit CTRL+A (for instance) and are in your configuration.
- Select the container configuration utility and
- Select the manage container menu.
- Now to repair the selected RAID5 set press CTRL+R and follow along on the screen.
- Once the repair is completed you will reboot.
- Login
- Open “My Computer” the “missing” drive should reappear.
PLEASE NOTE AGAIN: You will have corrupt data even if this has succeeded. you will now want to identify what drive caused the initial failure (initially in a failed or degraded state) and the next drive that fail/degraded causing the RAID5 to be in a FAILED state. Replace those drives.
Again, if you need help, I am a consultant and available. 
Hope this helps!