Upgrading Mirrored Hard Drives on Dell PowerEdge T110 II Server

Respectfully, a lot of problems with the previous post.   (First, i have developers NDA, so am quite familiar with the firmware).
 1. The controller couldn't care less about make / model. There is NOTHING in the firmware that looks at that.  If a disk isn't supported, it is going to be for other reasons.

2. The 48-bit LBA registry setting makes zero sense.  The controller makes the logical volume emulate a SCSI drive.  48-bit LBA is applicable to the ATA/SATA instruction set, not the SCSI instruction set.

3. As i wrote before, the biggest incompatibility issue is if you try to use a disk with anything but 512 byte sector size; or if total # of sectors > 2^32 -1, or if doing something other than RAID1 and the total number of usable logical blocks is > 2^32 -1 .

No, you can just take it out of the tray - it is the exact same drive.

Once you do, your VD will be the same size, and the S-series controllers do not have any way of expanding the VD to fill the new drives. That's why backup/restore is your only option here.

No, this isn't a question of partitions. We are talking about the Virtual Disk size, which is essentially the "disk" size that is being made available to the OS. The equivalent on a desktop would be upgrading a 500GB disk to a 1TB disk using Gparted instead of replacing the disk with a larger one. The VD is the "disk" that the OS can see, so you must make the VD larger before the OS can see it (THEN that is when partitioning happens). Third-party utilities can't expand a RAID VD - only extend the partitions afterwards.

dlethe: I don't understand the tone of your response.  
It may well be that with your better knowledge of the firmware that you have good information.
However, I find your first assertion a bit shocking:

1. The controller couldn't care less about make / model. There is NOTHING in the firmware that looks at that.  If a disk isn't supported, it is going to be for other reasons.

Either the firmware you refer to is different that the one I encountered or what I did was what you would call "unusual".  I don't think it was.  Here's what I did:
I purchased a new 500GB Western Digital hard drive model WD5003AZLX and used it to replace a failing WD5003ABYX 500GB HD.  The system recognized it as an SSD and it was unusable in the RAID system.
I purchased a new 500GB Western Digital hard drive model WD5003ABYX with the model number matching what was being replaced.  This worked.

I realize that this is empirical data and only a single data point.  Yet, that's what happened.
Perhaps it would be good for others to know why?  I sure don't.

As far as the 48-bit LBA: as I said, I didn't try it.  These ARE SATA drives and I can only conclude that it's necessary for them to be recognized in the system properly before the SCSI emulation can happen.  The RAID system will not accept what the system sees as an SSD.  They aren't recognized in the system properly without the registry edit as I understand it.  It's a topic that's easy to research if necessary.

You replaced a WD RE4 (RAID Edition) with a WD Black. Black is designed as a desktop/laptop consumer-grade drive and should not be used in RAID arrays or servers. Non-certified, non-enterprise grade drives can display a number of quirks because of incompatibility.

The Virtual Disk manages two separate disks in a mirrored configuration on the hardware/controller side, but it presents the single Virtual Disk it manages to the OS to use. The OS is oblivious to number of disks in the array or that there is even an array present.

Only Dell software can speak to the controller to query what devices it is managing. This is ABSOLUTELY a supported feature of Dell controllers, but the S-series controllers are the bottom-of-the-barrel when it comes to controllers and do not support expansion in this way. The H-series controllers do. I would always recommend the H7x0 controller for any application. Even Windows mirroring would be preferable to the S-series controllers.

PowerEdgeTech: do you mean me?  

You replaced a WD RE4 (RAID Edition) with a WD Black.

I replaced a WD5003ABYX with the same WD5003ABYX.  I'm not aware that there are different models with the same model number.  So I'm confused. It would be nice to know.

I thought it was the author, but I was addressing your comment:

I purchased a new 500GB Western Digital hard drive model WD5003AZLX and used it to replace a failing WD5003ABYX 500GB HD.  The system recognized it as an SSD and it was unusable in the RAID system.
I purchased a new 500GB Western Digital hard drive model WD5003ABYX with the model number matching what was being replaced.  This worked.

I realize that this is empirical data and only a single data point.  Yet, that's what happened.
Perhaps it would be good for others to know why?  I sure don't.

You said you used a WD5003AZLX (WD Black https://www.newegg.com/Product/Product.aspx?Item=N82E16822236345) to replace a failing WD5003ABYX (WD RE4 https://www.amazon.com/Enterprise-Drive-Cache-WD5003ABYX-Model/dp/B003SALVN4), which you said didn't work. You said it worked to replace the RE4 with another RE4, which makes sense. The RE4 is not certified by Dell, but the older RE4's were validated by WD on Dell controllers. You said you didn't know why it didn't work ... now you do :)

Fred Marshall - My response was simply to correct the mistakes in your post.  I sincerely apologize as clearly interpreted my response as something that had a "tone".   I'm just blunt, and don't read anything else into it other than that.

It looks like PowerEdgeTech handled the reasons nicely on why Black vs RE4 change.
As for the 48-bit thing,  the controller presents the LUN as a SCSI device.  The O/S does not see individual disks, and certainly not ATA/IDE/SATA drives.    

P.S.  USB sticks are the same way, they emulate SCSI devices.