OK, I ordered the following:
Western Digital Drive kit for WD Sentinel 2 Cache 3.5-Inch Internal Bare or OEM Drives (WDBNSH0020HNC-NASN)
This is the exact match needed for my DX4000. Running latest firmware, have all updates and update rollup installed.
I slide this new drive in as shown, and after several hours my display shows nothing new (not showing “Rebuilding” like it should) Dashboard shows RAID 1. Drive 1 as Normal, Drive 2 as Normal and Drive 3 as New Drive.
I have another exact same unit and added a drive to it last week. Within 5 minutes of inserting a new drive in that unit, the display shows rebuilding. But on this problem unit it never does.
Called support and they are as dumb as a fence post. Took three tries explaining this. After second time, they repeat my problem, “so you are trying to backup your Sentinel?” Hello! Then they tell me I need to download the Server Recovery ISO.
Recover what? The server boots and works just will not utilize the new drive and convert RAID from RAID 1 to RAID 5.