If your controller presents multiple logical drives (/dev/sda, /dev/sdb, /dev/sdc), then /dev/sda may contain physical disks with IDs 0,1,2 and /dev/sdb may contain physical disks with IDs 3,4,5. The N value is controller-wide, not per logical drive. So you can usually access all physical disks through any logical device, but safest is to use the logical drive that belongs to the same RAID group. When in doubt, try all N on /dev/sda.
Better: use storcli to see which PD belongs to which DG (drive group / logical drive).
Some guides suggest -d sat+megaraid,N for SATA drives behind a MegaRAID. Try -d megaraid,N first; if that fails, -d sat+megaraid,N may work for some older firmware.
Here’s a bash one-liner to check all physical disks on the first controller:
for pd in 0..15; do smartctl -H -d megaraid,$pd /dev/sda &>/dev/null; if [ $? -eq 0 ]; then echo "PD $pd OK"; else echo "PD $pd missing or error"; fi; done
On Debian/Ubuntu:
sudo apt install smartmontools
On RHEL/CentOS:
sudo yum install smartmontools
The error smartctl open device: /dev/sda failed: DELL or MegaRAID controller, please try adding -d megaraid,N is not a bug—it is a sign that you need to tell smartctl which physical drive behind the RAID controller to query.
Key takeaways:
By mastering the -d megaraid,N parameter, you can unlock full S.M.A.R.T. visibility on your Dell or MegaRAID-based servers, allowing proactive drive replacement and preventing unexpected data loss.
Further Reading:
If you found this article helpful, share it with fellow sysadmins struggling with RAID and S.M.A.R.T. on Dell or MegaRAID controllers.
This error occurs when smartctl cannot directly access a physical disk (/dev/sda) because the disk is behind a Dell PERC or MegaRAID controller. The OS sees a virtual drive, not the raw physical disk.
Here’s a concise review of the problem and solution:
The error is not a bug – it's a deliberate safety mechanism. The RAID controller hides physical disks by design. Using -d megaraid,N is the correct, supported, and safe method to query SMART data on Dell PERC and LSI MegaRAID controllers. Ignoring this flag risks querying the wrong device or corrupting the RAID metadata.
Always use:
smartctl -a -d megaraid,<physical_disk_id> /dev/sda
This error occurs because the LSI MegaRAID controller hides physical drives behind a virtual RAID volume . To access individual drive health data, you must tell which specific physical slot to query. If your controller presents multiple logical drives (
(device type) flag to specify the controller type and the physical drive index ( Command Syntax: sudo smartctl -a -d megaraid,N /dev/sda Use code with caution. Copied to clipboard : Displays all SMART information. -d megaraid,N : Points to the cap N raised to the t h power physical drive (starting at 0). : The logical device handle for the RAID controller. Step-by-Step Guide 1. Find the Physical Drive Index (
You need to identify which physical slot number corresponds to your drive. Use the MegaRAID management tool (like ) to list physical drives: # If using MegaCli sudo MegaCli -PDList -aALL | grep "Device Id" # If using perccli (common on newer Dell servers) sudo perccli /c0 /eall /sall show Use code with caution. Copied to clipboard Look for the "Device ID" "Slot Number" 2. Run the Smartctl Command Once you have the ID (e.g., sudo smartctl -x -d megaraid,0 /dev/sda Use code with caution. Copied to clipboard 3. Handling SATA Drives
If your drives are SATA (rather than SAS) behind a MegaRAID controller, you may need a combined device type: sudo smartctl -a -d sat+megaraid,N /dev/sda Use code with caution. Copied to clipboard Troubleshooting Tips Permissions : Always run these commands with or as root. Outdated Software megaraid,N still fails, ensure you are using a recent version of smartmontools Drive Handle
: Even if you have multiple physical drives, you usually use the same logical handle (e.g., ) for all of them; the part is what differentiates the physical disks. MegaCli commands to check for specific media or predictive failure errors? Check for Megaraid (and other Physical disk/raid) problems
This error occurs because the operating system sees your RAID controller (e.g., a LSI MegaRAID
) as a single logical device, effectively hiding the physical health data of the individual drives behind it
cannot "see through" the controller by default, it fails to open The Fix: Using the -d megaraid,N To access a specific physical drive, you must tell which "slot" or it occupies on the controller. Identify the Device ID ( Use a RAID management tool like
to find the physical drive IDs. For many Dell servers, the first drive is often ID Run the corrected command: with your drive's ID and run the command with sudo smartctl -a -d megaraid,N /dev/sda Use code with caution. Copied to clipboard Example for the first drive: sudo smartctl -a -d megaraid,0 /dev/sda For SATA drives behind the controller: You may need sat+megaraid,N www.couyon.net Why this happens
Resolving smartctl "Open Device Failed" on Dell MegaRAID Controllers
If you encounter the error Smartctl open device: /dev/sda failed: DELL or MegaRaid controller, please try adding '-d megaraid,N', it means smartctl cannot directly talk to your hard drives because they are hidden behind a RAID controller (like a Dell PERC). To fix this, you must tell smartctl exactly which physical drive to look at using the -d megaraid,N flag. Why This Error Occurs
Standard Linux device names like /dev/sda often represent Virtual Disks (logical volumes) created by the RAID controller, not the physical hardware. Since SMART data exists on the physical disks themselves, smartctl needs to bypass the RAID abstraction layer. Step-by-Step Solution 1. Find the Physical Drive IDs
To use the correct N value, you first need to identify the Device ID (DID) assigned by the controller.
Option A: Using smartctl scanRun this command to see a list of physical drives the system can detect:smartctl --scanThis often returns lines like /dev/bus/0 -d megaraid,0.
Option B: Using MegaCLI or StorCLIIf you have Dell/LSI management tools installed, use them for more detail:storcli /c0 /eall /sall show (Look for the DID column).MegaCli -pdlist -a0 | grep "Device Id". 2. Run the Correct smartctl Command
Once you have the ID (e.g., 0, 1, or 32), use the -d (device type) flag: For SAS/SCSI Drives:smartctl -a -d megaraid,0 /dev/sda For SATA Drives:smartctl -a -d sat+megaraid,0 /dev/sda Some guides suggest -d sat+megaraid,N for SATA drives
Note: Replace 0 with your actual Device ID and /dev/sda with your controller's device node. Troubleshooting Common Issues Smartmontools with MegaRAID Controller - Thomas-Krenn.AG
This error occurs because your controller hides the physical drive's SMART data behind a RAID layer . To fix it, you must tell which specific physical disk ID to query. 🛠️ The Direct Fix Run the command using the -d megaraid,N flag, where is the drive's physical ID (starting from 0). Try this first (for the first drive): sudo smartctl -a -d megaraid,0 /dev/sda Use code with caution. Copied to clipboard 🔍 How to find the correct ID (N) megaraid,0
doesn't work, use one of these methods to find the actual physical drive IDs: sudo smartctl --scan
to see a list of detected drives and their corresponding IDs. Use MegaCLI / StorCLI (Dell Recommended):
If you have the RAID management tools installed, you can list all physical drives and their Device IDs sudo storcli /c0 /eall /sall show (Look at the "DID" column). sudo megacli -pdlist -a0 | grep "Device Id" Server Fault 💡 Common Variations
Depending on your drive type (SATA vs. SAS) and controller version, you might need a slightly different flag: For SATA drives behind MegaRAID: sudo smartctl -a -d sat+megaraid,0 /dev/sda Using the SCSI generic path: still fails, try the generic bus path: sudo smartctl -a -d megaraid,0 /dev/bus/0 If you are using a very old version of smartmontools , consider updating it
(version 7.0 or higher is recommended) as newer versions have significantly better support for Dell PERC and LSI MegaRAID controllers. Unix & Linux Stack Exchange If you'd like, let me know: server model (e.g., Dell PowerEdge R730) you're using. smartctl --scan If you're trying to monitor a
Fix: smartctl "Open Device Failed" on Dell or MegaRAID Controllers
When running smartctl on a Dell PowerEdge server or any system using a MegaRAID (LSI/Broadcom) controller, you often encounter this error:Smartctl open device: /dev/sda failed: Dell or MegaRAID controller, please try adding '-d megaraid,N'.
This happens because the operating system sees a virtual logical drive (the RAID array), but smartctl needs to talk directly to the physical disks hidden behind the controller. The Solution: Using the -d megaraid,N Flag
To bypass the virtual layer, you must tell smartctl which specific physical disk you want to inspect by providing its Device ID (represented as 1. Find the Physical Device ID (
You cannot guess this number, as it doesn't always start at 0. Use the storcli (or older MegaCli) utility to find the DID (Device ID). Command: sudo storcli /c0 /eall /sall show
What to look for: Locate the DID column in the "Drive Information" table. If your disk is in slot 1 and has a DID of 11, then 2. Run the Correct smartctl Command
Once you have the ID, run the command against the controller's device node (usually /dev/sda or /dev/bus/0). Cannot get smartctl working - Unix & Linux Stack Exchange
Error: Smartctl Open Device Failed
When attempting to run smartctl, a popular command-line utility for monitoring and managing disk drives, on a Linux system, you might encounter an error message similar to:
smartctl open device /dev/sda failed: Dell or MegaRAID controller. Please try adding '-d megaraid,N'
This error typically occurs when smartctl is unable to directly access the disk drive /dev/sda due to the presence of a RAID controller, specifically a Dell or MegaRAID controller.
Understanding the Issue
The error message suggests that the disk drive is behind a RAID controller, which is a hardware component that manages multiple disk drives as a single logical unit. In this case, the controller is a Dell or MegaRAID device. The smartctl utility needs to communicate with the disk drive through this controller, but it doesn't know how to do so by default.
Solution: Specifying the RAID Controller
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.
Here's an example:
smartctl -d megaraid,0 /dev/sda
In this example, 0 is the logical drive number (N) associated with the disk drive /dev/sda. You may need to adjust this value depending on your specific configuration.
Finding the Logical Drive Number
To find the logical drive number, you can use the megacli command, which is a utility provided by LSI (now part of Broadcom) for managing MegaRAID controllers.
Here's an example:
megacli -ldinfo -lall
This command will display information about all logical drives configured on the MegaRAID controller. Look for the logical drive number associated with the disk drive you want to monitor.
Additional Tips
By following these steps and adding the -d megaraid,N option to the smartctl command, you should be able to successfully monitor and manage your disk drives behind a Dell or MegaRAID controller. On Debian/Ubuntu:
sudo apt install smartmontools
"smartctl open device dev sda failed dell or megaraid controller please try adding -d megaraid,N"
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.