Welcome to the Dell Community @bulaqi 

EDITED: Removed reference to wrong manual.

Best regards,

U2

As mentioned above, typically this option is called "SATA Operation", and despite the name it also affects NVMe SSDs.  If you can't find that, then Dell may have changed the name of that option in newer systems.  I haven't used an Inspiron 7490 specifically.

Yes, i can find following options in another Latitude 7490 laptop    

• Disabled
• AHCI
• RAID On: This option is enabled by default.

But, unfortunately, these options was changed in Inspiron 7490, only 2 options are  

• Disabled
• RAID On: This option is enabled by default.

I really can't undestand why dell change this key feature. Or there is another item in other place can do same thing?

Jesse L,

   Thanks for your supporting.

   I did all steps as your suggestion: turn off interface -> disabled SATA controller -> switch interface back on.

   But, things still can't run lucky . Contents in 'Device information' show:

        Type = (none) and device = (none).

   During bootup,  a popup waring was shown:

            SupportAssist was able to identify a possible issue with your system..

           warning message: Hard Drive - Not installed.

    Boot OS from USB disk, system also can't find the hard drive.

bulaqi,

If you switch the storage interface to off can you then select disable and then switch it back on. What does it do?  Let me know. If this does not work I will need to contact a level 2 technician to see if this is by default and not able to change.

bulaqi,

Start the computer and tap the F2 key to enter the bios. Choose the option to restore defaults ,save the changes and exit. Is th hard drive seen in the bios? Also, start the computer and tap the F12 key and choose to run the ePSA Diags. Post back with any failures.

This has worked for many people over the years. Please be sure to create a Full disk Image before attempting.

https://www.tenforums.com/customization/104898-switch-raid-ahci.html

The correct way to switch from RAID to AHCI is to make the BIOS changes then, USe Disk Part to Clean your Disk/SSD and then  Do a Clean install to the AHCI disk/SSD

It is important to use Diskpart to Clean your Disk/SSD prior to completing the Clean Instll, The easist way is to start the clean install once you get to the part where you need to select a volume to install too. Press Shift and F10 this will bring up a comand prompt type in

Diskpart

Select the disk you want to Clean," it should be the only disk you have connected"

Type Clean

after clean is complete your Disk/SSD will be in RAW condition exactly as it first came from the factory

Type Exit

Your Disk/SSD should now be available as a volume to install too.

@bulaqi  just out of curiosity, have you tried Disabled?  I'm wondering if Dell changed the meaning of that option so that "Disabled" now just means "RAID Mode Disabled", i.e. AHCI mode, instead of disabling the interface entirely. I would be surprised if they removed AHCI mode, but I could see them removing an option to disable the entire interface since that's not typically necessary.

Yes, i have tried the action to "Disabled". but unlucky, it does NOT means "RAID Mode Disabled", and use AHCI mode. It exactly disabled the disk fully, just as it's not plugged.

I' m so wondering and surprised this new 'FEATURE' now. and looking forward to finding a workaround.

I have restore the setting to 'Factory defaults' now. Still can't find the AHCI related items.