The DID value is the N you need for the megaraid,N flag.
The root cause of this error stems from structural virtualization. Under standard operating conditions, running smartctl -a /dev/sda forces the system to poll a standard block device node. However, when a machine utilizes an enterprise hardware controller—such as a Dell PERC (PowerEdge RAID Controller) Go to product viewer dialog for this item.
The article explains the error, why it happens, how to fix it, and includes best practices for monitoring RAID drives behind Dell PERC / MegaRAID controllers.
To resolve this issue, you need to inform smartctl about the presence of the MegaRAID controller and the logical drive number (N) associated with the disk drive you want to monitor. You can do this by adding the -d megaraid,N option to the smartctl command. The DID value is the N you need for the megaraid,N flag
In this case N=0 (device ID 0) and /dev/sda is the logical RAID volume. This should retrieve S.M.A.R.T. information for the first physical disk in the array. However, N=0 is not always the correct identifier; the actual device IDs can vary, as demonstrated in the following sections.
smartctl open device /dev/sda failed: DELL or MegaRAID controller, please try adding '-d megaraid,N'
) rather than the individual physical disks, smartctl cannot interpret the SMART data directly. However, when a machine utilizes an enterprise hardware
Once you have the ID (let’s assume it’s 4 ), run the command against your logical device (e.g., /dev/sda ): smartctl -a -d megaraid,4 /dev/sda Use code with caution. Copied to clipboard
If you’re managing a Dell PowerEdge server or any system equipped with an LSI/Avago MegaRAID or Dell PERC RAID controller, you’ve likely encountered this frustrating error when trying to check your disk health:
The value for N (the Device ID) is not always 0, 1, 2, etc. You can find the correct IDs using two methods: smartctl --scan Use code with caution. Copied to clipboard You can do this by adding the -d
❌ Standard Request: [ smartctl ] ----> [ /dev/sda (Logical Volume) ] ----> [ RAID Controller ] --X--> [ Physical Drives ] Correct Path: [ smartctl -d megaraid,0 ] ----> [ Pass-through Command ] ----> [ Controller Enclosure ] ----> [ Physical Drive 0 ]
=== START OF READ SMART DATA SECTION === SMART Health Status: OK
=== START OF READ SMART DATA SECTION === SMART Status not supported: ATA return descriptor not supported by controller firmware